code: static <K, V1, V2> Function<Entry<K, V1>, Entry<K, V2>> asEntryToEntryFunction(
        final EntryTransformer<? super K, ? super V1, V2> transformer) {
      checkNotNull(transformer);
      return new Function<Entry<K, V1>, Entry<K, V2>>() {
        @Override
        public Entry<K, V2> apply(final Entry<K, V1> entry) {
          return transformEntry(transformer, entry);
        }
      };
    }
docs: Views an entry transformer as a function from entries to entries.