protected function config(string $operator, string $key = null)
    {
        if (isset($this->mutators[$operator])) {
            return is_null($key) ? $this->mutators[$operator] : $this->mutators[$operator][$key];
        }
    }
protected function config(string $operator, string $key = null)
    {
        if (isset($this->mutators[$operator])) {
            return is_null($key) ? $this->mutators[$operator] : $this->mutators[$operator][$key];
        }
    }
protected function config ( string $ operator , string $ key = null ) { if ( isset ( $ this -> mutators [ $ operator ] ) ) { return is_null ( $ key ) ? $ this -> mutators [ $ operator ] : $ this -> mutators [ $ operator ] [ $ key ] ; } }
Get mutator config.

@param string $operator
@param string $key

@return mixed
Get mutator config .