docs: protected void validate() {
      Preconditions.checkState(
          (mMultiImageRequests == null) || (mImageRequest == null),
          "Cannot specify both ImageRequest and FirstAvailableImageRequests!");
      Preconditions.checkState(
          (mDataSourceSupplier == null) ||
              (mMultiImageRequests == null && mImageRequest == null && mLowResImageRequest == null),
          "Cannot specify DataSourceSupplier with other ImageRequests! Use one or the other.");
    }