/**
  * @param Dialog $dialog
  * @return Dialog
  */
 public function add(Dialog $dialog)
 {
     $dialog->setTelegram($this->telegram);
     // save new dialog
     $chatId = $dialog->getChat()->getId();
     $this->setField($chatId, 'next', $dialog->getNext());
     $this->setField($chatId, 'dialog', get_class($dialog));
     // @todo It's not safe. Need to define Dialogs registry with check of bindings
     return $dialog;
 }