def _changeGroupImage(self, image_id, thread_id=None):
        """
        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
        """
        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
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