code: private void indent(TaskListener listener, int depth) {
          for (int i = 0; i < depth; i++) {
              listener.getLogger().print(' ');
          }
      }
docs: TODO create a PR on jenkins-core to make {@link hudson.model.Cause.UpstreamCause#indent(TaskListener, int)} protected instead of private
  and delete this method once the PR is merged
  
  @see UpstreamCause#print(TaskListener)