code: @SuppressWarnings("WeakerAccess")
      @UiThread
      public boolean popCurrentController() {
          ThreadUtils.ensureMainThread();
  
          RouterTransaction transaction = backstack.peek();
          if (transaction == null) {
              throw new IllegalStateException("Trying to pop the current controller when there are none on the backstack.");
          }
          return popController(transaction.controller);
      }
docs: Pops the top {@link Controller} from the backstack
  
  @return Whether or not this Router still has controllers remaining on it after popping.