code: def update(self, body=values.unset, attributes=values.unset):
          
          return self._proxy.update(body=body, attributes=attributes, )
docs: Update the MessageInstance
  
          :param unicode body: The new message body string.
          :param unicode attributes: The new attributes metadata field you can use to store any data you wish.
  
          :returns: Updated MessageInstance
          :rtype: twilio.rest.chat.v1.service.channel.message.MessageInstance