code: def send_webapi(self, text, attachments=None, as_user=True, thread_ts=None):
          
          self._client.send_message(
              self._body['channel'],
              text,
              attachments=attachments,
              as_user=as_user,
              thread_ts=thread_ts)
docs: Send a reply using Web API
  
              (This function supports formatted message
              when using a bot integration)