/// <summary>
/// Removes a <see cref="VertexType"/> from this graph. An exception is thrown if the <see cref="VertexType"/> is in use.
/// </summary>
/// <param name="type">a <see cref="VertexType"/> instance</param>
public void RemoveVertexType(VertexType type)
{
if (type.GetVertices().ElementAtOrDefault(0) != null)
{
throw new VertexTypeInUseException();
}
if (type.subType.Count > 0)
{
throw new VertexTypeInUseException();
}
type.Unpersist(Session);
}