'Acknowledge a message by sending a receipt.
Arguments:
msg -- The message to acknowledge.'

def ack(self, msg):

    ack = self.xmpp.Message()
    ack['to'] = msg['from']
    ack['from'] = msg['to']
    ack['receipt'] = msg['id']
    ack['id'] = msg['id']
    ack.send()
