new_contents: from vtk import *
  
  graph = vtkMutableDirectedGraph()
  a = graph.AddVertex()
  b = graph.AddChild(a)
  c = graph.AddChild(a)
  d = graph.AddChild(b)
  e = graph.AddChild(c)
  f = graph.AddChild(c)
  
  tree = vtkTree()
  tree.CheckedShallowCopy(graph)
  
  view = vtkGraphLayoutView()
  view.AddRepresentationFromInput(tree)
  
  window = vtkRenderWindow()
  window.SetSize(600, 600)
  view.SetupRenderWindow(window)
  window.GetInteractor().Start()
  
  
subject: Add a Python example of creating a tree.