code: private boolean goBackTo(final ContentScene contentScene) {
          final int index;
  
          if (mContentSceneViewStack.isEmpty()
                  || (index = mContentSceneViewStack.indexOf(contentScene)) == -1) {
              return false;
          }
  
          for (int i = 0; i < index; ++i) {
              mContentSceneViewStack.pop();
          }
  
          return true;
      }
docs: stack