src/precore/util/Optional.php
public static function ofNullable($nullableReference) : Optional
    {
        return $nullableReference === null
            ? Optional::absent()
            : Optional::of($nullableReference);
    }
public static function ofNullable($nullableReference) : Optional
    {
        return $nullableReference === null
            ? Optional::absent()
            : Optional::of($nullableReference);
    }
If nullableReference is non-null, returns an {@link Optional} instance containing that
reference; otherwise returns {@link Optional::absent}.

@param $nullableReference
@return Optional