Creates a new message to be sent or stored

        :param str resource: Custom resource to be used in this message
         (Defaults to parent main_resource)
        :return: New empty message
        :rtype: Message

def new_message(self, resource=None):
        """ Creates a new message to be sent or stored

        :param str resource: Custom resource to be used in this message
         (Defaults to parent main_resource)
        :return: New empty message
        :rtype: Message
        """
        return Message(parent=self, main_resource=resource, is_draft=True)