code: public function addVoter(VoterInterface $voter)
      {
          @trigger_error(sprintf('The %s() method is deprecated since version 2.3 and will be removed in 3.0. Pass voters in the constructor instead.', __METHOD__), E_USER_DEPRECATED);
  
          if ($this->voters instanceof \Traversable) {
              $this->voters = iterator_to_array($this->voters);
          }
  
          $this->voters[] = $voter;
      }
docs: Adds a voter in the matcher.
  
  If an iterator was used to provide voters in the constructor, it will be
  converted to array when using this method, breaking any potential lazy-loading.
  
  @deprecated since 2.3. Pass voters in the constructor instead.
  
  @param VoterInterface $voter