code: public function addClass($class)
      {
          $classes = $this->getClasses();
  
          if (!in_array($class, $classes)) {
              $classes[] = $class;
          }
  
          $this->setClasses($classes);
  
          return $this;
      }
docs: Adds the css classes to the view.
  
  @param string $class
  
  @return $this