protected function _alias($alias, $conditions, $multipleNulls)
    {
        $aliased = [];
        foreach ($conditions as $key => $value) {
            if ($multipleNulls) {
                $aliased["$alias.$key"] = $value;
            } else {
                $aliased["$alias.$key IS"] = $value;
            }
        }

        return $aliased;
    }