public function whereIn($field, $param, string $op = ''): self
    {
        $ops = ['?'];
        if (is_array($param)) {
            $ops = array_fill(0, count($param), '?');
        }

        return $this->where($this->prepareField($field) .' IN ('. join(', ', $ops) .')', $param, $op);
    }