docs: function filterTree (obj, iterate, options, context) {
    var result = []
    if (obj && iterate) {
      context = context || this
      eachTree(obj, function (item, index, items, path, parent) {
        if (iterate.call(context, item, index, items, path, parent)) {
          result.push(item)
        }
      }, options)
    }
    return result
  }