code: public function reply($message)
      {
          if (is_string($message)) {
              $this->messages[] = Text::create()
                  ->text($message)
                  ->setAgentVersion($this->agentVersion)
                  ->setRequestSource($this->requestSource);
  
              if (! $this->doesSupportRichMessage()) {
                  $this->text = $message;
              }
          } elseif ($message instanceof RichMessage) {
              if (! $this->doesSupportRichMessage()) {
                  $this->text = $message->getFallbackText();
              }
  
              $message->setAgentVersion($this->agentVersion)
                  ->setRequestSource($this->requestSource);
  
              $this->messages[] = $message;
          } elseif ($message instanceof Conversation) {
              $this->messages[] = Payload::create($message->render())
                  ->setAgentVersion($this->agentVersion)
                  ->setRequestSource($this->requestSource);
          }
  
          return $this;
      }
docs: Response to incoming request.
  
  @param string|\Dialogflow\Richmessage|\Dialogflow\Action\Conversation $message
  
  @return \Dialogflow\WebhookClient