old_contents: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  
  def make_set():
  	pass
  
  
  def link():
  	pass
  
  
  def find():
  	pass
  
  
  def union():
  	pass
  
  
  def kruskal():
  	"""Kruskal's algorithm for minimum spanning tree 
  	in weighted graph.
  
      Time complexity for graph G(V, E): 
          O(|E|+|V|+|E|log(|V|)) 
          = O(|E|log(|V|^2)) 
          = O(|E|log(|V|)).
  	"""
  	pass
  
  
  def main():
  	w_graph_d = {
          'a': {'b': 1, 'd': 4, 'e': 3},
          'b': {'a': 1, 'd': 4, 'e': 2},
          'c': {'e': 4, 'f': 5},
          'd': {'a': 4, 'b': 4, 'e': 4},
          'e': {'a': 3, 'b': 2, 'c': 4, 'd': 4, 'f': 7},
          'f': {'c': 5, 'e': 7}
      }
      print('w_graph_d:\n{}'.format(w_graph_d))
  
      print('Kruskal\'s minimum spanning tree:')
      pass
  
  
  if __name__ == '__main__':
  	main()
  
new_contents: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  
  def make_set():
  	pass
  
  
  def link():
  	pass
  
  
  def find():
  	pass
  
  
  def union():
  	pass
  
  
  def kruskal():
  	"""Kruskal's algorithm for minimum spanning tree 
  	in weighted undirected graph.
  
      Time complexity for graph G(V, E): 
          O(|E|+|V|+|E|log(|V|)) 
          = O(|E|log(|V|^2)) 
          = O(|E|log(|V|)).
  	"""
  	pass
  
  
  def main():
  	w_graph_d = {
          'a': {'b': 1, 'd': 4, 'e': 3},
          'b': {'a': 1, 'd': 4, 'e': 2},
          'c': {'e': 4, 'f': 5},
          'd': {'a': 4, 'b': 4, 'e': 4},
          'e': {'a': 3, 'b': 2, 'c': 4, 'd': 4, 'f': 7},
          'f': {'c': 5, 'e': 7}
      }
      print('w_graph_d:\n{}'.format(w_graph_d))
  
      print('Kruskal\'s minimum spanning tree:')
      pass
  
  
  if __name__ == '__main__':
  	main()
  
subject: Revise doc string by adding "undirected"