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