public function nullsFirst() : Ordering
    {
        return Ordering::from(Collections::comparatorFrom(
            function ($object1, $object2) {
                return $object1 === null
                    ? -1
                    : ($object2 === null
                        ? 1
                        : $this->compare($object1, $object2));
            }
        ));
    }
public function nullsFirst() : Ordering
    {
        return Ordering::from(Collections::comparatorFrom(
            function ($object1, $object2) {
                return $object1 === null
                    ? -1
                    : ($object2 === null
                        ? 1
                        : $this->compare($object1, $object2));
            }
        ));
    }
Returns an ordering that treats null as less than all other values and uses this to compare non-null values.

@return Ordering