code: def _add_url(self, chunk):
          
          if 'url' in chunk:
              return chunk
          public_path = chunk.get('publicPath')
          if public_path:
              chunk['url'] = public_path
          else:
              fullpath = posixpath.join(self.state.static_view_path,
                                        chunk['name'])
              chunk['url'] = self._request.static_url(fullpath)
          return chunk
docs: Add a 'url' property to a chunk and return it