original_string: public function addListener(Listener $listener) : void {
          $this->listeners = $this->listeners->add($listener);
      }
code: public function addListener(Listener $listener) : void {
          $this->listeners = $this->listeners->add($listener);
      }
code_tokens: public function addListener ( Listener $ listener ) : void { $ this -> listeners = $ this -> listeners -> add ( $ listener ) ; }
docstring: add an event listener to the dispatcher
  
  @param Listener $listener
docstring_tokens: add an event listener to the dispatcher