code: def _changeGroupImage(self, image_id, thread_id=None):
          
          thread_id, thread_type = self._getThread(thread_id, None)
  
          data = {"thread_image_id": image_id, "thread_id": thread_id}
  
          j = self._post(self.req_url.THREAD_IMAGE, data, fix_request=True, as_json=True)
          return image_id
docs: Changes a thread image from an image id
  
          :param image_id: ID of uploaded image
          :param thread_id: User/Group ID to change image. See :ref:`intro_threads`
          :raises: FBchatException if request failed