docs: public static <E, T> Page<T> createPage(final Page<? extends E> sourcePage,
                                              final PageEntryTransformer<T, E> transformer) {
          if (sourcePage == null) {
              return null;
          }
          if (transformer == null) {
              return cast(sourcePage);
          }
          return createPage(sourcePage.getEntries(), sourcePage.getPageRequest(), sourcePage.getTotalSize(), transformer);
      }