kibana-123/src/ui/public/agg_response/hierarchical/_collect_keys.js

Kibana is an open source (Apache Licensed), browser based analytics and search dashboard for Elasticsearch. Kibana is a snap to setup and start using. Kibana strives to be easy to get started with, while also being flexible and powerful, just like Elastic

import _ from 'lodash';
export default function collectKeys(children) {
  let nextChildren = _.pluck(children, 'children');
  let keys = _.pluck(children, 'name');
  return _(nextChildren)
  .map(collectKeys)
  .flattenDeep()
  .union(keys)
  .value();
};