enum

Optional. Possible values of the field. This field can be used to restrict a value to a fixed set of values. To mark a field as an enum, set format to enum and provide the list of possible values in enum. For example: 1. To define directions: {type:STRING, format:enum, enum:["EAST", "NORTH", "SOUTH", "WEST"]} 2. To define apartment numbers: {type:INTEGER, format:enum, enum:["101", "201", "301"]}