public static <T> Predicate<T> equalTo(@Nullable Object target) {
        return target == null ? Objects::isNull : target::equals;
    }
Returns a predicate which returns true if the target is
{@link Object#equals(Object)} to the input. If the target is null,
the predicate returns true if the input is also null, false otherwise.

@param target the target object to compare against
@param <T> the type
@return a predicate
helper/src/main/java/me/lucko/helper/function/Predicates.java