docs: def _get_lecture_asset_ids(self, course_id, video_id):
          """
          Obtain a list of asset ids from a lecture.
          """
          dom = get_page(self._session, OPENCOURSE_ONDEMAND_LECTURE_ASSETS_URL,
                         json=True, course_id=course_id, video_id=video_id)
          # Note that we extract here "id", not definition -> assetId, as it
          # be extracted later.
          return [asset['id']
                  for asset in dom['linked']['openCourseAssets.v1']]