Evaluate unsupervised GraphSAGE without labels

In the example https://github.com/dmlc/dgl/blob/master/examples/pytorch/graphsage/train_sampling_unsupervised.py, the dataset has labeled nodes. Are these labels necessary or we can just avoid the function evaluate?
Without these labels, how can we assess the accuracy of the model?

Thanks.

You can use link-prediction metrics like MRR, Hit@k.