code: public function render()
      {
          $out = [];
  
          $out['expectUserResponse'] = $this->expectUserResponse;
  
          $items = [];
          $suggestions = [];
          $linkOutSuggestion = null;
          foreach ($this->messages as $message) {
              if ($message instanceof ResponseInterface) {
                  $item = $message->renderRichResponseItem();
  
                  if ($item) {
                      $items[] = $item;
                  }
              }
  
              if ($message instanceof SuggestionInterface) {
                  $rendered = $message->renderRichResponseSuggestion();
  
                  if (is_array($rendered)) {
                      foreach ($rendered as $suggestion) {
                          $suggestions[] = ['title' => $suggestion];
                      }
                  } elseif (is_string($rendered)) {
                      $suggestions[] = ['title' => $rendered];
                  } else {
                      // do nothing
                  }
              }
  
              if ($message instanceof LinkOutSuggestionInterface) {
                  $linkOutSuggestion = $message->renderRichResponseLinkOutSuggestion();
              }
  
              if ($message instanceof QuestionInterface) {
                  if ($item = $message->renderRichResponseItem()) {
                      $items[] = $item;
                  }
              }
          }
  
          $out['richResponse']['items'] = $items;
  
          if (count($suggestions) > 0) {
              $out['richResponse']['suggestions'] = $suggestions;
          }
  
          if ($linkOutSuggestion) {
              $out['richResponse']['linkOutSuggestion'] = $linkOutSuggestion;
          }
  
          $systemIntent = null;
          foreach ($this->messages as $message) {
              if ($message instanceof QuestionInterface) {
                  $systemIntent = $message->renderSystemIntent();
              }
          }
  
          if ($systemIntent) {
              $out['systemIntent'] = $systemIntent;
          }
  
          return $out;
      }
docs: Render response as array.
  
  @return array