code: def layout_route(self, request):
      r
      body = self.layout_impl()
      return http_util.Respond(request, body, 'application/json')
docs: r"""Fetches the custom layout specified by the config file in the logdir.
  
      If more than 1 run contains a layout, this method merges the layouts by
      merging charts within individual categories. If 2 categories with the same
      name are found, the charts within are merged. The merging is based on the
      order of the runs to which the layouts are written.
  
      The response is a JSON object mirroring properties of the Layout proto if a
      layout for any run is found.
  
      The response is an empty object if no layout could be found.