private function getTransformation()
    {
        $transforms = [];
        foreach ($this->fields as $field => $extra) {
            if (is_int($field)) {
                $transforms[$extra] = $extra;
                continue;
            }
            
            $transform = (key_exists('transform', $extra)) ? $extra['transform'] : $field;
            
            if ($transform === false) {
                continue;
            }
            
            $transforms[$field] = $transform;
        }
        
        return $transforms;
    }