protected function checkRuleCorrect($rule)
    {
        if (!isset($rule->value)) {
            // We will assume a missing value for the rule is to be interpreted as empty.
            $rule->value = null;
        }
        if (!isset($rule->id, $rule->field, $rule->type, $rule->input, $rule->operator)) {
            return false;
        }
        if (!isset($this->operators[$rule->operator])) {
            return false;
        }

        return true;
    }