public function isPotentiallyEmpty(ExpressionInterface $expression)
 {
     /** @var RegexExpression $expression */
     $parser = new RegexParser($expression->getRegex());
     $able_to_match_empty_string = $parser->parse("") !== null;
     return $able_to_match_empty_string;
 }
 public function compile(ExpressionInterface $expression)
 {
     /** @var RegexExpression $expression */
     return new RegexParser($expression->getRegex());
 }