code: def create(self, text=None, attachments=None, source_guid=None):
          
          message = {
              'source_guid': source_guid or str(time.time()),
          }
  
          if text is not None:
              message['text'] = text
  
          if attachments is not None:
              message['attachments'] = [a.to_json() for a in attachments]
  
          payload = {'message': message}
          response = self.session.post(self.url, json=payload)
          message = response.data['message']
          return Message(self, **message)
docs: Create a new message in the group.
  
          :param str text: the text of the message
          :param attachments: a list of attachments
          :type attachments: :class:`list`
          :param str source_guid: a unique identifier for the message
          :return: the created message
          :rtype: :class:`~groupy.api.messages.Message`