This will convert alternate representations of CAR process structure into (adj, weights, num) form required by dcar_normal. Two alternate representations are handled:
as.carAdjacency(...)
Either: a symmetric matrix of un-normalized weights, or two lists specifying adjacency indices and the corresponding un-normalized weights.
A single matrix argument will be interpreted as a matrix of symmetric un-normalized weights;
Two lists will be interpreted as (the first) a list of numeric vectors specifying the adjacency (neighboring) indices of each CAR process component, and (the second) a list of numeric vectors giving the un-normalized weights for each of these neighboring relationships.