code: def post_message(session, thread_id, message):
      
      headers = {
          'Content-Type': 'application/x-www-form-urlencoded'
      }
      message_data = {
          'message': message,
      }
  
      # POST /api/messages/0.1/threads/{thread_id}/messages/
      endpoint = 'threads/{}/messages'.format(thread_id)
      response = make_post_request(session, endpoint, headers,
                                   form_data=message_data)
      json_data = response.json()
      if response.status_code == 200:
          return Message(json_data['result'])
      else:
          raise MessageNotCreatedException(message=json_data['message'],
                                           error_code=json_data['error_code'],
                                           request_id=json_data['request_id'])
docs: Add a message to a thread