def __init__(self, oauth2session, client_type, client_config):
        """
        Args:
            oauth2session (requests_oauthlib.OAuth2Session):
                The OAuth 2.0 session from ``requests-oauthlib``.
            client_type (str): The client type, either ``web`` or
                ``installed``.
            client_config (Mapping[str, Any]): The client
                configuration in the Google `client secrets`_ format.

        .. _client secrets:
            https://developers.google.com/api-client-library/python/guide
            /aaa_client_secrets
        """
        self.client_type = client_type
        """str: The client type, either ``'web'`` or ``'installed'``"""
        self.client_config = client_config[client_type]
        """Mapping[str, Any]: The OAuth 2.0 client configuration."""
        self.oauth2session = oauth2session
        """requests_oauthlib.OAuth2Session: The OAuth 2.0 session."""