/// <summary>
/// Creates and returns an edge which connects two
/// vertex in a direct manner.
/// </summary>
/// <param name="from"></param>
/// <param name="to"></param>
/// <returns></returns>
public Edge CreateEdge(Vertex from, Vertex to)
{
Edge edge = new Edge(from, to);
m_edges.Add(edge);
from.AddSuccessor(to);
return edge;
}