Compute Engine API . machineTypes

Instance Methods

aggregatedList(project, filter=None, includeAllScopes=None, maxResults=None, orderBy=None, pageToken=None, returnPartialSuccess=None, serviceProjectNumber=None, x__xgafv=None)

Retrieves an aggregated list of machine types. To prevent failure, Google recommends that you set the `returnPartialSuccess` parameter to `true`.

aggregatedList_next()

Retrieves the next page of results.

close()

Close httplib2 connections.

get(project, zone, machineType, x__xgafv=None)

Returns the specified machine type.

list(project, zone, filter=None, maxResults=None, orderBy=None, pageToken=None, returnPartialSuccess=None, x__xgafv=None)

Retrieves a list of machine types available to the specified project.

list_next()

Retrieves the next page of results.

Method Details

aggregatedList(project, filter=None, includeAllScopes=None, maxResults=None, orderBy=None, pageToken=None, returnPartialSuccess=None, serviceProjectNumber=None, x__xgafv=None)
Retrieves an aggregated list of machine types. To prevent failure, Google recommends that you set the `returnPartialSuccess` parameter to `true`.

Args:
  project: string, Project ID for this request. (required)
  filter: string, A filter expression that filters resources listed in the response. Most Compute resources support two types of filter expressions: expressions that support regular expressions and expressions that follow API improvement proposal AIP-160. These two types of filter expressions cannot be mixed in one request. If you want to use AIP-160, your expression must specify the field name, an operator, and the value that you want to use for filtering. The value must be a string, a number, or a boolean. The operator must be either `=`, `!=`, `>`, `<`, `<=`, `>=` or `:`. For example, if you are filtering Compute Engine instances, you can exclude instances named `example-instance` by specifying `name != example-instance`. The `:*` comparison can be used to test whether a key has been defined. For example, to find all objects with `owner` label use: ``` labels.owner:* ``` You can also filter nested fields. For example, you could specify `scheduling.automaticRestart = false` to include instances only if they are not scheduled for automatic restarts. You can use filtering on nested fields to filter based on resource labels. To filter on multiple expressions, provide each separate expression within parentheses. For example: ``` (scheduling.automaticRestart = true) (cpuPlatform = "Intel Skylake") ``` By default, each expression is an `AND` expression. However, you can include `AND` and `OR` expressions explicitly. For example: ``` (cpuPlatform = "Intel Skylake") OR (cpuPlatform = "Intel Broadwell") AND (scheduling.automaticRestart = true) ``` If you want to use a regular expression, use the `eq` (equal) or `ne` (not equal) operator against a single un-parenthesized expression with or without quotes or against multiple parenthesized expressions. Examples: `fieldname eq unquoted literal` `fieldname eq 'single quoted literal'` `fieldname eq "double quoted literal"` `(fieldname1 eq literal) (fieldname2 ne "literal")` The literal value is interpreted as a regular expression using Google RE2 library syntax. The literal value must match the entire field. For example, to filter for instances that do not end with name "instance", you would use `name ne .*instance`. You cannot combine constraints on multiple fields using regular expressions.
  includeAllScopes: boolean, Indicates whether every visible scope for each scope type (zone, region, global) should be included in the response. For new resource types added after this field, the flag has no effect as new resource types will always include every visible scope for each scope type in response. For resource types which predate this field, if this flag is omitted or false, only scopes of the scope types where the resource type is expected to be found will be included.
  maxResults: integer, The maximum number of results per page that should be returned. If the number of available results is larger than `maxResults`, Compute Engine returns a `nextPageToken` that can be used to get the next page of results in subsequent list requests. Acceptable values are `0` to `500`, inclusive. (Default: `500`)
  orderBy: string, Sorts list results by a certain order. By default, results are returned in alphanumerical order based on the resource name. You can also sort results in descending order based on the creation timestamp using `orderBy="creationTimestamp desc"`. This sorts results based on the `creationTimestamp` field in reverse chronological order (newest result first). Use this to sort resources like operations so that the newest operation is returned first. Currently, only sorting by `name` or `creationTimestamp desc` is supported.
  pageToken: string, Specifies a page token to use. Set `pageToken` to the `nextPageToken` returned by a previous list request to get the next page of results.
  returnPartialSuccess: boolean, Opt-in for partial success behavior which provides partial results in case of failure. The default value is false. For example, when partial success behavior is enabled, aggregatedList for a single zone scope either returns all resources in the zone or no resources, with an error code.
  serviceProjectNumber: string, The Shared VPC service project id or service project number for which aggregated list request is invoked for subnetworks list-usable api.
  x__xgafv: string, V1 error format.
    Allowed values
      1 - v1 error format
      2 - v2 error format

Returns:
  An object of the form:

    {
  "id": "A String", # [Output Only] Unique identifier for the resource; defined by the server.
  "items": { # A list of MachineTypesScopedList resources.
    "a_key": { # [Output Only] Name of the scope containing this set of machine types.
      "machineTypes": [ # [Output Only] A list of machine types contained in this scope.
        { # Represents a Machine Type resource. You can use specific machine types for your VM instances based on performance and pricing requirements. For more information, read Machine Types.
          "accelerators": [ # [Output Only] A list of accelerator configurations assigned to this machine type.
            {
              "guestAcceleratorCount": 42, # Number of accelerator cards exposed to the guest.
              "guestAcceleratorType": "A String", # The accelerator type resource name, not a full URL, e.g. nvidia-tesla-t4.
            },
          ],
          "architecture": "A String", # [Output Only] The architecture of the machine type.
          "bundledLocalSsds": { # [Output Only] The configuration of bundled local SSD for the machine type.
            "defaultInterface": "A String", # The default disk interface if the interface is not specified.
            "partitionCount": 42, # The number of partitions.
          },
          "creationTimestamp": "A String", # [Output Only] Creation timestamp in RFC3339 text format.
          "deprecated": { # Deprecation status for a public resource. # [Output Only] The deprecation status associated with this machine type. Only applicable if the machine type is unavailable.
            "deleted": "A String", # An optional RFC3339 timestamp on or after which the state of this resource is intended to change to DELETED. This is only informational and the status will not change unless the client explicitly changes it.
            "deprecated": "A String", # An optional RFC3339 timestamp on or after which the state of this resource is intended to change to DEPRECATED. This is only informational and the status will not change unless the client explicitly changes it.
            "obsolete": "A String", # An optional RFC3339 timestamp on or after which the state of this resource is intended to change to OBSOLETE. This is only informational and the status will not change unless the client explicitly changes it.
            "replacement": "A String", # The URL of the suggested replacement for a deprecated resource. The suggested replacement resource must be the same kind of resource as the deprecated resource.
            "state": "A String", # The deprecation state of this resource. This can be ACTIVE, DEPRECATED, OBSOLETE, or DELETED. Operations which communicate the end of life date for an image, can use ACTIVE. Operations which create a new resource using a DEPRECATED resource will return successfully, but with a warning indicating the deprecated resource and recommending its replacement. Operations which use OBSOLETE or DELETED resources will be rejected and result in an error.
            "stateOverride": { # A rollout policy configuration. # The rollout policy for this deprecation. This policy is only enforced by image family views. The rollout policy restricts the zones where the associated resource is considered in a deprecated state. When the rollout policy does not include the user specified zone, or if the zone is rolled out, the associated resource is considered in a deprecated state. The rollout policy for this deprecation is read-only, except for allowlisted users. This field might not be configured. To view the latest non-deprecated image in a specific zone, use the imageFamilyViews.get method.
              "defaultRolloutTime": "A String", # An optional RFC3339 timestamp on or after which the update is considered rolled out to any zone that is not explicitly stated.
              "locationRolloutPolicies": { # Location based rollout policies to apply to the resource. Currently only zone names are supported and must be represented as valid URLs, like: zones/us-central1-a. The value expects an RFC3339 timestamp on or after which the update is considered rolled out to the specified location.
                "a_key": "A String",
              },
            },
          },
          "description": "A String", # [Output Only] An optional textual description of the resource.
          "guestCpus": 42, # [Output Only] The number of virtual CPUs that are available to the instance.
          "id": "A String", # [Output Only] The unique identifier for the resource. This identifier is defined by the server.
          "isSharedCpu": True or False, # [Output Only] Whether this machine type has a shared CPU. See Shared-core machine types for more information.
          "kind": "compute#machineType", # [Output Only] The type of the resource. Always compute#machineType for machine types.
          "maximumPersistentDisks": 42, # [Output Only] Maximum persistent disks allowed.
          "maximumPersistentDisksSizeGb": "A String", # [Output Only] Maximum total persistent disks size (GB) allowed.
          "memoryMb": 42, # [Output Only] The amount of physical memory available to the instance, defined in MB.
          "name": "A String", # [Output Only] Name of the resource.
          "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
          "selfLinkWithId": "A String", # [Output Only] Server-defined URL for this resource with the resource id.
          "zone": "A String", # [Output Only] The name of the zone where the machine type resides, such as us-central1-a.
        },
      ],
      "warning": { # [Output Only] An informational warning that appears when the machine types list is empty.
        "code": "A String", # [Output Only] A warning code, if applicable. For example, Compute Engine returns NO_RESULTS_ON_PAGE if there are no results in the response.
        "data": [ # [Output Only] Metadata about this warning in key: value format. For example: "data": [ { "key": "scope", "value": "zones/us-east1-d" }
          {
            "key": "A String", # [Output Only] A key that provides more detail on the warning being returned. For example, for warnings where there are no results in a list request for a particular zone, this key might be scope and the key value might be the zone name. Other examples might be a key indicating a deprecated resource and a suggested replacement, or a warning about invalid network settings (for example, if an instance attempts to perform IP forwarding but is not enabled for IP forwarding).
            "value": "A String", # [Output Only] A warning data value corresponding to the key.
          },
        ],
        "message": "A String", # [Output Only] A human-readable description of the warning code.
      },
    },
  },
  "kind": "compute#machineTypeAggregatedList", # [Output Only] Type of resource. Always compute#machineTypeAggregatedList for aggregated lists of machine types.
  "nextPageToken": "A String", # [Output Only] This token allows you to get the next page of results for list requests. If the number of results is larger than maxResults, use the nextPageToken as a value for the query parameter pageToken in the next list request. Subsequent list requests will have their own nextPageToken to continue paging through the results.
  "selfLink": "A String", # [Output Only] Server-defined URL for this resource.
  "unreachables": [ # [Output Only] Unreachable resources.
    "A String",
  ],
  "warning": { # [Output Only] Informational warning message.
    "code": "A String", # [Output Only] A warning code, if applicable. For example, Compute Engine returns NO_RESULTS_ON_PAGE if there are no results in the response.
    "data": [ # [Output Only] Metadata about this warning in key: value format. For example: "data": [ { "key": "scope", "value": "zones/us-east1-d" }
      {
        "key": "A String", # [Output Only] A key that provides more detail on the warning being returned. For example, for warnings where there are no results in a list request for a particular zone, this key might be scope and the key value might be the zone name. Other examples might be a key indicating a deprecated resource and a suggested replacement, or a warning about invalid network settings (for example, if an instance attempts to perform IP forwarding but is not enabled for IP forwarding).
        "value": "A String", # [Output Only] A warning data value corresponding to the key.
      },
    ],
    "message": "A String", # [Output Only] A human-readable description of the warning code.
  },
}
aggregatedList_next()
Retrieves the next page of results.

        Args:
          previous_request: The request for the previous page. (required)
          previous_response: The response from the request for the previous page. (required)

        Returns:
          A request object that you can call 'execute()' on to request the next
          page. Returns None if there are no more items in the collection.
        
close()
Close httplib2 connections.
get(project, zone, machineType, x__xgafv=None)
Returns the specified machine type.

Args:
  project: string, Project ID for this request. (required)
  zone: string, The name of the zone for this request. (required)
  machineType: string, Name of the machine type to return. (required)
  x__xgafv: string, V1 error format.
    Allowed values
      1 - v1 error format
      2 - v2 error format

Returns:
  An object of the form:

    { # Represents a Machine Type resource. You can use specific machine types for your VM instances based on performance and pricing requirements. For more information, read Machine Types.
  "accelerators": [ # [Output Only] A list of accelerator configurations assigned to this machine type.
    {
      "guestAcceleratorCount": 42, # Number of accelerator cards exposed to the guest.
      "guestAcceleratorType": "A String", # The accelerator type resource name, not a full URL, e.g. nvidia-tesla-t4.
    },
  ],
  "architecture": "A String", # [Output Only] The architecture of the machine type.
  "bundledLocalSsds": { # [Output Only] The configuration of bundled local SSD for the machine type.
    "defaultInterface": "A String", # The default disk interface if the interface is not specified.
    "partitionCount": 42, # The number of partitions.
  },
  "creationTimestamp": "A String", # [Output Only] Creation timestamp in RFC3339 text format.
  "deprecated": { # Deprecation status for a public resource. # [Output Only] The deprecation status associated with this machine type. Only applicable if the machine type is unavailable.
    "deleted": "A String", # An optional RFC3339 timestamp on or after which the state of this resource is intended to change to DELETED. This is only informational and the status will not change unless the client explicitly changes it.
    "deprecated": "A String", # An optional RFC3339 timestamp on or after which the state of this resource is intended to change to DEPRECATED. This is only informational and the status will not change unless the client explicitly changes it.
    "obsolete": "A String", # An optional RFC3339 timestamp on or after which the state of this resource is intended to change to OBSOLETE. This is only informational and the status will not change unless the client explicitly changes it.
    "replacement": "A String", # The URL of the suggested replacement for a deprecated resource. The suggested replacement resource must be the same kind of resource as the deprecated resource.
    "state": "A String", # The deprecation state of this resource. This can be ACTIVE, DEPRECATED, OBSOLETE, or DELETED. Operations which communicate the end of life date for an image, can use ACTIVE. Operations which create a new resource using a DEPRECATED resource will return successfully, but with a warning indicating the deprecated resource and recommending its replacement. Operations which use OBSOLETE or DELETED resources will be rejected and result in an error.
    "stateOverride": { # A rollout policy configuration. # The rollout policy for this deprecation. This policy is only enforced by image family views. The rollout policy restricts the zones where the associated resource is considered in a deprecated state. When the rollout policy does not include the user specified zone, or if the zone is rolled out, the associated resource is considered in a deprecated state. The rollout policy for this deprecation is read-only, except for allowlisted users. This field might not be configured. To view the latest non-deprecated image in a specific zone, use the imageFamilyViews.get method.
      "defaultRolloutTime": "A String", # An optional RFC3339 timestamp on or after which the update is considered rolled out to any zone that is not explicitly stated.
      "locationRolloutPolicies": { # Location based rollout policies to apply to the resource. Currently only zone names are supported and must be represented as valid URLs, like: zones/us-central1-a. The value expects an RFC3339 timestamp on or after which the update is considered rolled out to the specified location.
        "a_key": "A String",
      },
    },
  },
  "description": "A String", # [Output Only] An optional textual description of the resource.
  "guestCpus": 42, # [Output Only] The number of virtual CPUs that are available to the instance.
  "id": "A String", # [Output Only] The unique identifier for the resource. This identifier is defined by the server.
  "isSharedCpu": True or False, # [Output Only] Whether this machine type has a shared CPU. See Shared-core machine types for more information.
  "kind": "compute#machineType", # [Output Only] The type of the resource. Always compute#machineType for machine types.
  "maximumPersistentDisks": 42, # [Output Only] Maximum persistent disks allowed.
  "maximumPersistentDisksSizeGb": "A String", # [Output Only] Maximum total persistent disks size (GB) allowed.
  "memoryMb": 42, # [Output Only] The amount of physical memory available to the instance, defined in MB.
  "name": "A String", # [Output Only] Name of the resource.
  "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
  "selfLinkWithId": "A String", # [Output Only] Server-defined URL for this resource with the resource id.
  "zone": "A String", # [Output Only] The name of the zone where the machine type resides, such as us-central1-a.
}
list(project, zone, filter=None, maxResults=None, orderBy=None, pageToken=None, returnPartialSuccess=None, x__xgafv=None)
Retrieves a list of machine types available to the specified project.

Args:
  project: string, Project ID for this request. (required)
  zone: string, The name of the zone for this request. (required)
  filter: string, A filter expression that filters resources listed in the response. Most Compute resources support two types of filter expressions: expressions that support regular expressions and expressions that follow API improvement proposal AIP-160. These two types of filter expressions cannot be mixed in one request. If you want to use AIP-160, your expression must specify the field name, an operator, and the value that you want to use for filtering. The value must be a string, a number, or a boolean. The operator must be either `=`, `!=`, `>`, `<`, `<=`, `>=` or `:`. For example, if you are filtering Compute Engine instances, you can exclude instances named `example-instance` by specifying `name != example-instance`. The `:*` comparison can be used to test whether a key has been defined. For example, to find all objects with `owner` label use: ``` labels.owner:* ``` You can also filter nested fields. For example, you could specify `scheduling.automaticRestart = false` to include instances only if they are not scheduled for automatic restarts. You can use filtering on nested fields to filter based on resource labels. To filter on multiple expressions, provide each separate expression within parentheses. For example: ``` (scheduling.automaticRestart = true) (cpuPlatform = "Intel Skylake") ``` By default, each expression is an `AND` expression. However, you can include `AND` and `OR` expressions explicitly. For example: ``` (cpuPlatform = "Intel Skylake") OR (cpuPlatform = "Intel Broadwell") AND (scheduling.automaticRestart = true) ``` If you want to use a regular expression, use the `eq` (equal) or `ne` (not equal) operator against a single un-parenthesized expression with or without quotes or against multiple parenthesized expressions. Examples: `fieldname eq unquoted literal` `fieldname eq 'single quoted literal'` `fieldname eq "double quoted literal"` `(fieldname1 eq literal) (fieldname2 ne "literal")` The literal value is interpreted as a regular expression using Google RE2 library syntax. The literal value must match the entire field. For example, to filter for instances that do not end with name "instance", you would use `name ne .*instance`. You cannot combine constraints on multiple fields using regular expressions.
  maxResults: integer, The maximum number of results per page that should be returned. If the number of available results is larger than `maxResults`, Compute Engine returns a `nextPageToken` that can be used to get the next page of results in subsequent list requests. Acceptable values are `0` to `500`, inclusive. (Default: `500`)
  orderBy: string, Sorts list results by a certain order. By default, results are returned in alphanumerical order based on the resource name. You can also sort results in descending order based on the creation timestamp using `orderBy="creationTimestamp desc"`. This sorts results based on the `creationTimestamp` field in reverse chronological order (newest result first). Use this to sort resources like operations so that the newest operation is returned first. Currently, only sorting by `name` or `creationTimestamp desc` is supported.
  pageToken: string, Specifies a page token to use. Set `pageToken` to the `nextPageToken` returned by a previous list request to get the next page of results.
  returnPartialSuccess: boolean, Opt-in for partial success behavior which provides partial results in case of failure. The default value is false. For example, when partial success behavior is enabled, aggregatedList for a single zone scope either returns all resources in the zone or no resources, with an error code.
  x__xgafv: string, V1 error format.
    Allowed values
      1 - v1 error format
      2 - v2 error format

Returns:
  An object of the form:

    { # Contains a list of machine types.
  "id": "A String", # [Output Only] Unique identifier for the resource; defined by the server.
  "items": [ # A list of MachineType resources.
    { # Represents a Machine Type resource. You can use specific machine types for your VM instances based on performance and pricing requirements. For more information, read Machine Types.
      "accelerators": [ # [Output Only] A list of accelerator configurations assigned to this machine type.
        {
          "guestAcceleratorCount": 42, # Number of accelerator cards exposed to the guest.
          "guestAcceleratorType": "A String", # The accelerator type resource name, not a full URL, e.g. nvidia-tesla-t4.
        },
      ],
      "architecture": "A String", # [Output Only] The architecture of the machine type.
      "bundledLocalSsds": { # [Output Only] The configuration of bundled local SSD for the machine type.
        "defaultInterface": "A String", # The default disk interface if the interface is not specified.
        "partitionCount": 42, # The number of partitions.
      },
      "creationTimestamp": "A String", # [Output Only] Creation timestamp in RFC3339 text format.
      "deprecated": { # Deprecation status for a public resource. # [Output Only] The deprecation status associated with this machine type. Only applicable if the machine type is unavailable.
        "deleted": "A String", # An optional RFC3339 timestamp on or after which the state of this resource is intended to change to DELETED. This is only informational and the status will not change unless the client explicitly changes it.
        "deprecated": "A String", # An optional RFC3339 timestamp on or after which the state of this resource is intended to change to DEPRECATED. This is only informational and the status will not change unless the client explicitly changes it.
        "obsolete": "A String", # An optional RFC3339 timestamp on or after which the state of this resource is intended to change to OBSOLETE. This is only informational and the status will not change unless the client explicitly changes it.
        "replacement": "A String", # The URL of the suggested replacement for a deprecated resource. The suggested replacement resource must be the same kind of resource as the deprecated resource.
        "state": "A String", # The deprecation state of this resource. This can be ACTIVE, DEPRECATED, OBSOLETE, or DELETED. Operations which communicate the end of life date for an image, can use ACTIVE. Operations which create a new resource using a DEPRECATED resource will return successfully, but with a warning indicating the deprecated resource and recommending its replacement. Operations which use OBSOLETE or DELETED resources will be rejected and result in an error.
        "stateOverride": { # A rollout policy configuration. # The rollout policy for this deprecation. This policy is only enforced by image family views. The rollout policy restricts the zones where the associated resource is considered in a deprecated state. When the rollout policy does not include the user specified zone, or if the zone is rolled out, the associated resource is considered in a deprecated state. The rollout policy for this deprecation is read-only, except for allowlisted users. This field might not be configured. To view the latest non-deprecated image in a specific zone, use the imageFamilyViews.get method.
          "defaultRolloutTime": "A String", # An optional RFC3339 timestamp on or after which the update is considered rolled out to any zone that is not explicitly stated.
          "locationRolloutPolicies": { # Location based rollout policies to apply to the resource. Currently only zone names are supported and must be represented as valid URLs, like: zones/us-central1-a. The value expects an RFC3339 timestamp on or after which the update is considered rolled out to the specified location.
            "a_key": "A String",
          },
        },
      },
      "description": "A String", # [Output Only] An optional textual description of the resource.
      "guestCpus": 42, # [Output Only] The number of virtual CPUs that are available to the instance.
      "id": "A String", # [Output Only] The unique identifier for the resource. This identifier is defined by the server.
      "isSharedCpu": True or False, # [Output Only] Whether this machine type has a shared CPU. See Shared-core machine types for more information.
      "kind": "compute#machineType", # [Output Only] The type of the resource. Always compute#machineType for machine types.
      "maximumPersistentDisks": 42, # [Output Only] Maximum persistent disks allowed.
      "maximumPersistentDisksSizeGb": "A String", # [Output Only] Maximum total persistent disks size (GB) allowed.
      "memoryMb": 42, # [Output Only] The amount of physical memory available to the instance, defined in MB.
      "name": "A String", # [Output Only] Name of the resource.
      "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
      "selfLinkWithId": "A String", # [Output Only] Server-defined URL for this resource with the resource id.
      "zone": "A String", # [Output Only] The name of the zone where the machine type resides, such as us-central1-a.
    },
  ],
  "kind": "compute#machineTypeList", # [Output Only] Type of resource. Always compute#machineTypeList for lists of machine types.
  "nextPageToken": "A String", # [Output Only] This token allows you to get the next page of results for list requests. If the number of results is larger than maxResults, use the nextPageToken as a value for the query parameter pageToken in the next list request. Subsequent list requests will have their own nextPageToken to continue paging through the results.
  "selfLink": "A String", # [Output Only] Server-defined URL for this resource.
  "warning": { # [Output Only] Informational warning message.
    "code": "A String", # [Output Only] A warning code, if applicable. For example, Compute Engine returns NO_RESULTS_ON_PAGE if there are no results in the response.
    "data": [ # [Output Only] Metadata about this warning in key: value format. For example: "data": [ { "key": "scope", "value": "zones/us-east1-d" }
      {
        "key": "A String", # [Output Only] A key that provides more detail on the warning being returned. For example, for warnings where there are no results in a list request for a particular zone, this key might be scope and the key value might be the zone name. Other examples might be a key indicating a deprecated resource and a suggested replacement, or a warning about invalid network settings (for example, if an instance attempts to perform IP forwarding but is not enabled for IP forwarding).
        "value": "A String", # [Output Only] A warning data value corresponding to the key.
      },
    ],
    "message": "A String", # [Output Only] A human-readable description of the warning code.
  },
}
list_next()
Retrieves the next page of results.

        Args:
          previous_request: The request for the previous page. (required)
          previous_response: The response from the request for the previous page. (required)

        Returns:
          A request object that you can call 'execute()' on to request the next
          page. Returns None if there are no more items in the collection.