code: protected function renderV1()
      {
          if ('google' == $this->requestSource) {
              return [
                  'type'         => 'simple_response',
                  'platform'     => $this->requestSource,
                  'textToSpeech' => $this->text,
                  'displayText'  => $this->text,
              ];
          } else {
              $out = [
                  'type'   => self::v1MessageObjectText,
                  'speech' => $this->text,
              ];
  
              if (in_array($this->requestSource, $this->supportedRichMessagePlatforms)) {
                  $out['platform'] = $this->requestSource;
              }
  
              return $out;
          }
      }
docs: Render response as array for API V1.
  
  @return array