Redundant edges in NodeClassificationDataset about gcc HOT 1 CLOSED

Hi @jiangtanzju ,

Thanks for pointing out this. As you said, the double add_edges operations are not needed for those node classification datasets (Edgelist class). Initially we use this to ensure both node classification datasets and graph classification datasets (which are imported from DGL) are undirected. I double-checked after you proposed this issue and it turned out that these redundant operations do affect the results. Specifically, the accuracies on most datasets will be promoted a little bit after removing them properly. We will fix this in a later commit. Thanks for your contribution!

Best,

from gcc.