code: @Override
      public byte[] retrieveBytes(File impFi) {
          String fname = impFi.getName();
          int idx = fname.indexOf('.');
          if ( idx >= 0 ) {
              String ext = fname.substring(idx+1).toLowerCase();
              TranspilerHook transpilerHook = transpilerMap.get(ext);
              if ( transpilerHook != null ) {
                  return transpilerHook.transpile(impFi, this, new HashMap());
              }
          }
          return null;
      }
docs: invoke transpilers during prodmode inlining
  @param impFi
  @return