/// <summary>
/// Gets the first adjacent vertex
/// </summary>
/// <param name="v">current vertex</param>
/// <returns>first out-vertex</returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="v"/> is a null reference
/// </exception>
public IVertex FirstChild(IVertex v)
{
if (v == null)
{
throw new ArgumentNullException("v");
}
return(Traversal.FirstTargetVertex(this.Wrapped.OutEdges(v)));
}