code: public function delete(...$args) {
          $this->open();
  
          foreach ($args as $key) {
              unset($this->_data[$key]);
          }
  
          return $this;
      }
docs: Removes a variable in the session array.
  
  $session->delete('foo');
  
  @param   string $key,... variable name
  @return  $this