defaultEnvironmentVariables

Returns the default environment variables for the client. Supported environment variables:

• googleApiKey -> GOOGLE_API_KEY environment variable.
• geminiApiKey -> GEMINI_API_KEY environment variable.
• project -> GOOGLE_CLOUD_PROJECT: Project ID for Vertex AI APIs.
• location -> GOOGLE_CLOUD_LOCATION: Location for Vertex AI APIs.
• vertexAI -> GOOGLE_GENAI_USE_VERTEXAI: Whether to use Vertex AI APIs(true or false).
• geminiBaseUrl -> GOOGLE_GEMINI_BASE_URL: Base URL for Gemini APIs.
• vertexBaseUrl -> GOOGLE_VERTEX_BASE_URL: Base URL for Vertex AI APIs.