Some validation masks appear completely black

[liushihowe]

I am using the ImageNet-S dataset and noticed that some validation mask images appear completely black. For example:

ImageNetS50\validation-segmentation\n01443537\ILSVRC2012_val_00028713.png

I wanted to confirm whether this is expected behavior. Does a completely black mask indicate that the image has no pixel-level annotations, or could this be an issue with the dataset?

Thank you for your help!