Send the message on the socket.
        
        Args:
            - message: the message to publish
            - message_type: the type of message being sent
            - topic: the topic on which to send the message. Defaults to ''.

def send(self,message,message_type,topic=''):
        """
        Send the message on the socket.
        
        Args:
            - message: the message to publish
            - message_type: the type of message being sent
            - topic: the topic on which to send the message. Defaults to ''.
        """
        if message_type == RAW:
            self._sock.send(message)
        elif message_type == PYOBJ:
            self._sock.send_pyobj(message)
        elif message_type == JSON:
            self._sock.send_json(message)
        elif message_type == MULTIPART:
            self._sock.send_multipart([topic, message])
        elif message_type == STRING:
            self._sock.send_string(message)
        elif message_type == UNICODE:
            self._sock.send_unicode(message)
        else:
            raise Exception("Unknown message type %s"%(message_type,))