docs: private static IonReader makeReader(IonCatalog catalog,
                                          UnifiedInputStreamX uis,
                                          int offset,
                                          _Private_LocalSymbolTableFactory lstFactory)
          throws IOException
      {
          IonReader r;
          if (has_binary_cookie(uis)) {
              r = new IonReaderBinaryUserX(catalog, lstFactory, uis, offset);
          }
          else {
              r = new IonReaderTextUserX(catalog, lstFactory, uis, offset);
          }
          return r;
      }