code: def submit_completion(self, block_key, completion):
          
          return BlockCompletion.objects.submit_completion(
              user=self._user,
              course_key=self._course_key,
              block_key=block_key,
              completion=completion
          )
docs: Submit a completion for the service user and course.
  
          Returns a (BlockCompletion, bool) where the boolean indicates
          whether the given BlockCompletion was newly created.