protected function normalizeConditionKeyword($key)
{
static $map = ['AND' => '$and', 'OR' => '$or', 'IN' => '$in', 'NOT IN' => '$nin'];
$matchKey = strtoupper($key);
if (array_key_exists($matchKey, $map)) {
return $map[$matchKey];
} else {
return $key;
}
}