code: private function collectChoicesAnswers($choices)
      {
          $answers = array();
          
          /* @var $choice \Symfony\Component\Form\ChoiceList\View\ChoiceView */
          foreach($choices as $choice) {
              if ($choice instanceof \Symfony\Component\Form\ChoiceList\View\ChoiceView) {
                  $answers[$choice->value] = $choice->label;
              } elseif ($choice instanceof \Symfony\Component\Form\ChoiceList\View\ChoiceGroupView) {
                  $answers = $answers + $this->collectChoicesAnswers($choice->choices);
              } else {
                  throw new \Exception(sprintf(
                          "The choice type is not know. Expected '%s' or '%s', get '%s'",
                          \Symfony\Component\Form\ChoiceList\View\ChoiceView::class,
                          \Symfony\Component\Form\ChoiceList\View\ChoiceGroupView::class,
                          get_class($choice)
                          ));
              }
          }
          
          return $answers;
      }
docs: Recursive method to collect the possibles answer from a ChoiceType (or
  its inherited types).
  
  @param \Symfony\Component\Form\FormInterface $form
  @return array where