code: private SearchableItem buildSearchableItem(Message menuItem) {
          return new SearchableItem((int) ((NumberField) menuItem.arguments.get(1)).getValue(),
                  ((StringField) menuItem.arguments.get(3)).getValue());
      }
docs: Creates a searchable item that represents a metadata field found for a track.
  
  @param menuItem the rendered menu item containing the searchable metadata field
  @return the searchable metadata field