protected function isAllowedKey($key): bool
    {
        return empty($this->allowedKeys) || \in_array($key, $this->allowedKeys, true);
    }
protected function isAllowedKey($key): bool
    {
        return empty($this->allowedKeys) || \in_array($key, $this->allowedKeys, true);
    }
protected function isAllowedKey ( $ key ) : bool { return empty ( $ this -> allowedKeys ) || \ in_array ( $ key , $ this -> allowedKeys , true ) ; }
Determine if a given key is permitted.

@param $key

@return bool
Determine if a given key is permitted .