def __init__(
      self,
      *,
      access_token: Optional[str] = None,
      service_account_json: Optional[str] = None,
  ):
    """Initializes the APIHubClient.

    You must set either access_token or service_account_json. This
    credential is used for sending request to API Hub API.

    Args:
        access_token: Google Access token. Generate with gcloud cli `gcloud auth
          print-access-token`. Useful for local testing.
        service_account_json: The service account configuration as a dictionary.
          Required if not using default service credential.
    """
    self.root_url = "https://apihub.googleapis.com/v1"
    self.credential_cache = None
    self.access_token, self.service_account = None, None

    if access_token:
      self.access_token = access_token
    elif service_account_json:
      self.service_account = service_account_json
Initializes the APIHubClient.

    You must set either access_token or service_account_json. This
    credential is used for sending request to API Hub API.

    Args:
        access_token: Google Access token. Generate with gcloud cli `gcloud auth
          print-access-token`. Useful for local testing.
        service_account_json: The service account configuration as a dictionary.
          Required if not using default service credential.
    
src/google/adk/tools/apihub_tool/clients/apihub_client.py