code: 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);
      }
docs: Transforms a page into another page.
  
  @param sourcePage  the source page
  @param transformer the entry transformer (may be {@code null} - than all entries
  of the source page will be added to the target page without
  transforming)
  @param <E>         source type of the page entries
  @param <T>         target type of the page entries
  @return the target page