public function build($ruleset = null): Validator
    {
        $validators = array_merge([], $this->validators);
        if (is_object($ruleset) || (is_array($ruleset) && Parser::isAssociative($ruleset))) {
            foreach ($ruleset as $field => $rules) {
                $validators[$field] = $this->parser->parse($rules);
            }
        }
        return new Validator($validators);
    }