code: def get_anchor_diff(anchor):
      
      new_anchor = make_anchor(
          file_path=anchor.file_path,
          offset=anchor.context.offset,
          width=len(anchor.context.topic),
          context_width=anchor.context.width,
          metadata=anchor.metadata)
  
      assert anchor.file_path == new_anchor.file_path
      assert anchor.context.offset == new_anchor.context.offset
      assert len(anchor.context.topic) == len(new_anchor.context.topic)
      assert anchor.metadata == new_anchor.metadata
  
      return tuple(
          _context_diff(
              anchor.file_path,
              anchor.context,
              new_anchor.context))
docs: Get the get_anchor_diff between an anchor and the current state of its source.
  
      Returns: A tuple of get_anchor_diff lines. If there is not different, then this
          returns an empty tuple.