code: def update(self, author=values.unset, attributes=values.unset,
                 date_created=values.unset, date_updated=values.unset,
                 body=values.unset):
          
          data = values.of({
              'Author': author,
              'Attributes': attributes,
              'DateCreated': serialize.iso8601_datetime(date_created),
              'DateUpdated': serialize.iso8601_datetime(date_updated),
              'Body': body,
          })
  
          payload = self._version.update(
              'POST',
              self._uri,
              data=data,
          )
  
          return MessageInstance(
              self._version,
              payload,
              session_sid=self._solution['session_sid'],
              sid=self._solution['sid'],
          )
docs: Update the MessageInstance
  
          :param unicode author: The identity of the message's author.
          :param unicode attributes: A string metadata field you can use to store any data you wish.
          :param datetime date_created: The date that this resource was created.
          :param datetime date_updated: The date that this resource was last updated.
          :param unicode body: The contents of the message.
  
          :returns: Updated MessageInstance
          :rtype: twilio.rest.messaging.v1.session.message.MessageInstance