code: public @Nullable Page getPage(@NotNull Predicate<Page> filter) {
      return getPage(filter, (Page)null);
    }
docs: Parse the suffix as page paths, return the first page from the suffix (relativ to the current page) that matches the given filter.
  
  @param filter a filter that selects only the page you're interested in.
  @return the page or null if no such page was selected by suffix