Support cugraph
I just noticed that networkx has a concept of "backends", which means that using cugraph is as easy as setting the NX_CUGRAPH_AUTOCONFIG=True environment variable. See https://github.com/rapidsai/nx-cugraph?tab=readme-ov-file#enabling-nx-cugraph for details.
I thought this might make things quicker when creating the graph. I had to make a few fixes thought to make it possible https://github.com/leifdenby/neural-lam/tree/feat/support-cugraph
This should go into weather-model-graphs eventually. But I just wanted to make a note of this until there is time to work on it and check whether it actually makes graph generation quicker.