Return an adjacency list of subnets
get_subnet_adj_list(adj_list)
An adjacency list where only the first node of a subnet contains the subnet and all other contain only the first node
A normal adjacency list
A graph with 4 components: 1, 2, 3, 4, and 5 and 6, 7, 8 would yield a list like so: 1: 2, 3, 4 2: 1 3: 1 4: 1 5: numeric(0) 6: 7, 8 7: 6, 8: 6
This format speeds up the construction of reachable sets on dense networks