/// <summary>
 /// search labels
 /// https://developer.github.com/v3/search/#search-labels
 /// </summary>
 /// <param name="search"></param>
 /// <returns>List of labels</returns>
 public IObservable <SearchLabelsResult> SearchLabels(SearchLabelsRequest search)
 {
     Ensure.ArgumentNotNull(search, nameof(search));
     return(_client.SearchLabels(search).ToObservable());
 }