code: def get_key_to_last_completed_course_block(user, course_key):
      
  
      last_completed_block = BlockCompletion.get_latest_block_completed(user, course_key)
  
      if last_completed_block is not None:
          return last_completed_block.block_key
  
      raise UnavailableCompletionData(course_key)
docs: Returns the last block a "user" completed in a course (stated as "course_key").
  
      raises UnavailableCompletionData when the user has not completed blocks in
      the course.
  
      raises UnavailableCompletionData when the visual progress waffle flag is
      disabled.