private function validValue($value, $operator)
    {
        if (! $this->validOperator($operator)) {
            return false; // @codeCoverageIgnore
        }

        if ($operator === "IN") {
            // Valid should be an array!
            return is_array($value);
        }
        if ($operator === "IS NOT") {
            return is_null($value);
        }

        return !is_array($value);
    }