@staticmethod
def validate_messages_for_send(message, app):
    """
        Makes sure that one or more messages have required fields for
        sending them by the sender.
        """
    if isinstance(message, (list, tuple, set)):
        result = True
        for m_one in message:
            result = result and m_one.valid_for_send(app)
    else:
        result = message.valid_for_send(app)
    return result
