/// <summary>
/// Creates Core vertex and related Visual vertex.
/// </summary>
/// <param name="x">X coordinate.</param>
/// <param name="y">Y coordinate.</param>
/// <param name="label">label of vertex</param>
public Vertex CreateVertex(double x, double y, string label = "")
{
Vertex v = new Vertex(x, y, label);
Vertices.Add(v);
visual.CreateVisualVertex(v);
return(v);
}
