public function move_bit(string $id, string $id_parent = null): ?bool
  { 
    if ( 
      \bbn\str::is_uid($id) && 
      (
        (\bbn\str::is_uid($id_parent) && $this->get_bit($id_parent)) || 
        \is_null($id_parent)
      ) &&
      ($bit = $this->get_bit($id)) &&
      ($cf = $this->get_class_cfg()) &&
      ($cfg =  $cf['arch']['user_options_bits'])
    ){
      $upd = [
        $cfg['id_parent'] => $id_parent,
        $cfg['num'] => $this->get_max_bit_num($bit[$cfg['id_user_option']], $id_parent, true)
      ];
      return !!$this->db->update($cf['tables']['user_options_bits'], $upd, [$cfg['id'] => $id]);
    }
    return null;
  }