[FAQ] GNNs frequent questions

Here is a collection of frequent questions about GNN models in BenchMARL

Here https://github.com/facebookresearch/BenchMARL/pull/161 is an example of using a GNN with a dynamic topology in VMAS

Start by reading the FAQ issue and the linked pull request 161, cited as an example of using a GNN with dynamic topology in VMAS. Determine which frequent GNN questions and answers belong in the collection; done means the FAQ covers the intended questions and includes the relevant example or link.

Written by the indexing model from the issue text.