code: @SuppressWarnings("unchecked")
    public static <K, V> ImmutableMap<K, V> of() {
      return (ImmutableMap<K, V>) RegularImmutableMap.EMPTY;
    }
docs: Returns the empty map. This map behaves and performs comparably to {@link
  Collections#emptyMap}, and is preferable mainly for consistency and maintainability of your
  code.