code: def overlay(overlay_name, dataset_uri, item_identifier):
      
      dataset = dtoolcore.DataSet.from_uri(dataset_uri)
      if overlay_name not in dataset.list_overlay_names():
          click.secho(
              "No such overlay in dataset: {}".format(overlay_name),
              fg="red",
              err=True
          )
          sys.exit(4)
      overlay = dataset.get_overlay(overlay_name)
  
      try:
          click.secho(str(overlay[item_identifier]))
      except KeyError:
          click.secho(
              "No such identifier in overlay: {}".format(item_identifier),
              fg="red",
              err=True
          )
          sys.exit(5)
docs: Return abspath to file with item content.
  
      Fetches the file from remote storage if required.