function readResourceUrl(node, objectStack) {
  const format = node.getAttribute('format');
  const template = node.getAttribute('template');
  const resourceType = node.getAttribute('resourceType');
  const resource = {};
  if (format) {
    resource['format'] = format;
  }
  if (template) {
    resource['template'] = template;
  }
  if (resourceType) {
    resource['resourceType'] = resourceType;
  }
  return resource;
}
@param {Element} node Node.
@param {Array<*>} objectStack Object stack.
@return {Object|undefined} Resource URL object.