Function to get Node from Diagram

There is a FindNodeForData method in PartManager:

Given some nodedata in a model, find the corresponding Node in this diagram.
How can I get Node if I have the key for the Node?

Given some data:

public class Employee : GraphModelNodeData<int> { public int Id { get; set; } public String Name { get; set; } . . . }
and a model using Employees:

var model = new GraphModel<Employee, int>(); model.NodesSource = ...;
you can find a particular Employee data:

      Employee emp = model.FindNodeByKey(123);

with which you can find the corresponding diagram Node:

      Node empnode = myDiagram.PartManager.FindNodeByData(emp);