@classmethod
def forget_client(mcs, attr_name_or_client):
    """
        Forget a `Client`.

        Args:
            attr_name_or_client: The client or the attr_name bound to forget.
        """
    if isinstance(attr_name_or_client, str):
        mcs._class_clients.pop(attr_name_or_client)
    else:
        mcs._class_clients.pop(attr_name_or_client.attr_name)
