The out degree of a vertex is the number of edges that originate at the vertex. The in degree of a vertex is the number of edges that terminate at the vertex. Modify the class DirectedGraph so that it...

The out degree of a vertex is the number of edges that originate at the vertex. The in degree of a vertex is the number of edges that terminate at the vertex. Modify the class DirectedGraph so that it can compute the in degree and out degree of any of its vertices.