docs: private Object lookUp(Class<?> type) {
          Jenkins j = Jenkins.getInstance();
          assert j != null : "This method is only invoked after the Jenkins singleton instance has been set";
          if (type==Jenkins.class || type==Hudson.class)
              return j;
          Injector i = j.getInjector();
          if (i!=null)
              return i.getInstance(type);
          throw new IllegalArgumentException("Unable to inject "+type);
      }