public function checkbox(string $name, string $locale = '') : string
{
$fieldName = $this->fieldName($name, $locale);
$contents = Form::checkbox($fieldName, 1, Form::useInitialValue($this->model, $name, $locale), ['class' => 'form-control']) . ' ' . fragment("back.{$this->module}.{$name}");
return $this->group([el('label.-checkbox', $contents)]);
}