code: func (w *Watcher) Query(query string) (*Handle, error) {
  	h := w.NewQuery(query)
  	return h, h.Start()
  }
docs: // Query registers a watch on the provided Rego query. Whenever changes are made to a
  // base or virtual document that the query depends on, an Event describing the new result
  // of the query will be sent through the Handle.
  //
  // Query will return an error if registering the watch fails for any reason.