Internal helper function to resolve either a node name or a
node index to a 0-based index using the Rust session.
.resolve_idx0_get expects a single value,
while .resolve_idx0_mget can return multiple values.
.resolve_idx0_get(session, node_name = NULL, node_index = NULL).resolve_idx0_mget(session, node_name = NULL, node_index = NULL)
A GraphSession pointer.
Optional character vector of node names.
Optional numeric vector of 1-based node indices.