docs: @Override
    public AbstractDraweeController build() {
      validate();
  
      // if only a low-res request is specified, treat it as a final request.
      if (mImageRequest == null && mMultiImageRequests == null && mLowResImageRequest != null) {
        mImageRequest = mLowResImageRequest;
        mLowResImageRequest = null;
      }
  
      return buildController();
    }