Removing edges cause previous NID overwritten

Hi,
After removing edges in subgraph, the NID was rearanged, and the original NID which maintain the node id in the large graph lost.
The following is the notebook.


I think dgl should give users a warning if they do something to transforme the graph struture while they have mantained NID and EID.

There is an similar issue of remove_edges. We changed the behavior in PR#2465 so that remove_edges and remove_nodes by default no longer generate dgl.NID and dgl.EID. Please install the latest the nightly-build and see if the problem has been fixed. Thanks!

Here we no longer generate dgl.NID means when user access this field, we will report a key error, or we will treat the subgraph as a normal graph, regenerate dgl.NID, drop its info in the whole graph?

It means remove_edges and remove_nodes will not generate a new NID or EID feature field and thus will not override any existing fields.