docs: @Override
      public Object transform( Object input ) {
  
          Map<String,Object> output = new HashMap<>();
  
          // Create a root LiteralPathElement so that # is useful at the root level
          MatchedElement rootLpe = new MatchedElement( ROOT_KEY );
          WalkedPath walkedPath = new WalkedPath();
          walkedPath.add( input, rootLpe );
  
          rootSpec.apply( ROOT_KEY, Optional.of( input ), walkedPath, output, null );
  
          return output.get( ROOT_KEY );
      }