code: public static <T> BulkheadOperator<T> of(Bulkhead bulkhead) {
          return of(bulkhead, Schedulers.parallel());
      }
docs: Creates a BulkheadOperator.
  
  @param <T>      the value type of the upstream and downstream
  @param bulkhead the Bulkhead
  @return a BulkheadOperator