# config/packages/twig.yaml
twig:
form_themes: ['bootstrap_4_layout.html.twig']{{ form_row(form.myRadio, {label_attr: {class: 'radio-custom'} }) }}
{{ form_row(form.myCheckbox, {label_attr: {class: 'checkbox-custom'} }) }}
{{ form_row(form.myCheckbox, {label_attr: {class: 'switch-custom'} }) }}Read more https://symfony.com/doc/4.4/form/bootstrap4.html