def __init__(self, service_account_email='default'):
        """
        Args:
            service_account_email (str): The service account email to use, or
                'default'. A Compute Engine instance may have multiple service
                accounts.
        """
        super(Credentials, self).__init__()
        self._service_account_email = service_account_email
def __init__ ( self , service_account_email = 'default' ) : super ( Credentials , self ) . __init__ ( ) self . _service_account_email = service_account_email
Args:
            service_account_email (str): The service account email to use, or
                'default'. A Compute Engine instance may have multiple service
                accounts.