code: public void invalidate() {
          if (mInvalid.compareAndSet(false, true)) {
              for (InvalidatedCallback callback : mOnInvalidatedCallbacks) {
                  callback.onInvalidated();
              }
          }
      }
docs: Signal the data source to stop loading, and notify its callback.
  <p>
  If invalidate has already been called, this method does nothing.