code: public static <K, V> Map.Entry<K, V> immutableEntry(Map.Entry<K, V> entry) {
        return new ImmutableEntry<>(entry);
     }
docs: Wraps a {@link Map.Entry}} with an immutable {@link Map.Entry}}. There is no copying involved.
  
  @param entry the mapping to wrap.
  @return an immutable {@link Map.Entry}} wrapper that delegates to the original mapping.