Dynamic/Types/DropdownMultiple.php
public function build(FormBuilderInterface $builder, FormField $field, $locale, $options)
    {
        $translation = $field->getTranslation($locale);
        $options['expanded'] = false;
        $options['multiple'] = true;
        $options = $this->getChoiceOptions($translation, $options);
        $type = ChoiceType::class;
        $builder->add($field->getKey(), $type, $options);
    }
public function build(FormBuilderInterface $builder, FormField $field, $locale, $options)
    {
        $translation = $field->getTranslation($locale);
        $options['expanded'] = false;
        $options['multiple'] = true;
        $options = $this->getChoiceOptions($translation, $options);
        $type = ChoiceType::class;
        $builder->add($field->getKey(), $type, $options);
    }
{@inheritdoc}