code: public function radioWithGap($options = [], $enclosedByLabel = true)
      {
          Html::addCssClass($options, $this->radioGapCssClass);
          return self::radio($options, $enclosedByLabel);
      }
docs: Creates radio button with gap
  @see http://materializecss.com/forms.html#radio
  @param array $options
  @param bool|true $enclosedByLabel
  @return $this