code: public function jsonSerialize()
      {
          $json = [];
  
          if (null !== $this->mediaId) {
              $json['mediaId'] = $this->mediaId;
          }
          if (null !== $this->imageTemplateId) {
              $json['imageTemplateId'] = $this->imageTemplateId;
          }
          if (null !== $this->videoTemplateId) {
              $json['videoTemplateId'] = $this->videoTemplateId;
          }
          if (null !== $this->documentTemplateId) {
              $json['documentTemplateId'] = $this->documentTemplateId;
          }
          if (null !== $this->audioTemplateId) {
              $json['audioTemplateId'] = $this->audioTemplateId;
          }
  
          return $json;
      }
docs: Gets all data that should be available in a json representation.
  
  @return array an associative array of the available variables