new_contents: from nose.tools import *
  
  import networkx as nx
  
  def test_unionfind():
      # Fixed by: 2cddd5958689bdecdcd89b91ac9aaf6ce0e4f6b8
      # Previously (in 2.x), the UnionFind class could handle mixed types.
      # But in Python 3.x, this causes a TypeError such as:
      #   TypeError: unorderable types: str() > int()
      #
      # Now we just make sure that no exception is raised.
      x = nx.utils.UnionFind()
      x.union(0, 'a')
  
subject: Add a test for UnionFind fix.