src/language-css/parser-postcss.js/parseNestedValue
function parseNestedValue(node) {
  if (node && typeof node === "object") {
    delete node.parent;
    for (const key in node) {
      parseNestedValue(node[key]);
      if (key === "nodes") {
        node.group = flattenGroups(parseValueNodes(node[key]));
        delete node[key];
      }
    }
  }
  return node;
}