def update(self, body=values.unset, attributes=values.unset):
data = values.of({'<STR_LIT>': body, '<STR_LIT>': attributes, })<EOL>payload = self._version.update(<EOL>'<STR_LIT:POST>',<EOL>self._uri,<EOL>data=data,<EOL>)<EOL>return MessageInstance(<EOL>self._version,<EOL>payload,<EOL>service_sid=self._solution['<STR_LIT>'],<EOL>channel_sid=self._solution['<STR_LIT>'],<EOL>sid=self._solution['<STR_LIT>'],<EOL>)<EOL>
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