Depth-First-Search

This is a code for depth first search. It creates a graph obect that you can add vertices and edges to. The DFS function returns a list of lists. This first list in the list is the root node/vertex. The second list are neighbors of the root node/vertex. The second list are nodes/vertices that are two path lengths away from the roots. And so on. You can alos print the adjacency list of the input graph.