feat: GenAI SDK client - Add api_key parameter to vertexai.Client`

PiperOrigin-RevId: 800051985

Author: yeesian

vertexai/_genai/client.py

@@ -122,6 +122,7 @@ class Client:
  def __init__(
  self,
  *,
+ api_key: Optional[str] = None,
  credentials: Optional[google.auth.credentials.Credentials] = None,
  project: Optional[str] = None,
  location: Optional[str] = None,
@@ -131,6 +132,9 @@ def __init__(
  """Initializes the client.
 
  Args:
+ api_key (str): The `API key
+ <https://cloud.google.com/vertex-ai/generative-ai/docs/start/express-mode/overview#api-keys>`_
+ to use for authentication. Applies to Vertex AI in express mode only.
  credentials (google.auth.credentials.Credentials): The credentials to use
  for authentication when calling the Vertex AI APIs. Credentials can be
  obtained from environment variables and default credentials. For more
@@ -156,6 +160,7 @@ def __init__(
 
  self._api_client = genai_client.Client._get_api_client(
  vertexai=True,
+ api_key=api_key,
  credentials=credentials,
  project=project,
  location=location,