code: @Override public Scope active() {
      BraveSpan span = currentSpan();
      if (span == null) return null;
      return new Scope() {
        @Override public void close() {
          // no-op
        }
  
        @Override public Span span() {
          return span;
        }
      };
    }
docs: This api's only purpose is to retrieve the {@link Scope#span() span}.
  
  Calling {@link Scope#close() close } on the returned scope has no effect on the active span