code: public static <E> Function<Object, E> constant(@NullableDecl E value) {
      return new ConstantFunction<E>(value);
    }
docs: Returns a function that ignores its input and always returns {@code value}.
  
  <p><b>Java 8 users:</b> use the lambda expression {@code o -> value} instead.
  
  @param value the constant value for the function to return
  @return a function that always returns {@code value}