function getSelector(parentNode) {
  const attributeMap = getAttributeMap(parentNode.attributes);

  if (attributeMap.has('id')) {
    return '#' + attributeMap.get('id');
  } else {
    const attrClass = attributeMap.get('class');
    if (attrClass) {
      return '.' + attrClass.split(/\s+/).join('.');
    }
  }

  return parentNode.nodeName.toLowerCase();
}
TODO: return unique selector, like axe-core does, instead of just id/class/name of a single node
@param {FailingNodeData['parentNode']} parentNode
@return {string}