code: public function actionFlush($category = null)
      {
          if (is_null($category)) {
              $category = $this->prompt("Category (blank for all): ");
          }
          if (empty($category)) {
              $category = 'all';
          } else {
              $category = ['category', $category];
          }
          Cacher::invalidateGroup($category);
          $this->out("Done!");
      }
docs: Flush the cache.
  
  @param string $category flush a particular category from cache [optional]