code: def minimum_spanning_subtree(self):
      '''Returns the (undirected) minimum spanning tree subgraph.'''
      dist = self.matrix('dense', copy=True)
      dist[dist==0] = np.inf
      np.fill_diagonal(dist, 0)
      mst = ssc.minimum_spanning_tree(dist)
      return self.__class__.from_adj_matrix(mst + mst.Tf minimum_spanning_subtree(self):
      '''Returns the (undirected) minimum spanning tree subgraph.'''
      dist = self.matrix('dense', copy=True)
      dist[dist==0] = np.inf
      np.fill_diagonal(dist, 0)
      mst = ssc.minimum_spanning_tree(dist)
      return self.__class__.from_adj_matrix(mst + mst.T)
docs: Returns the (undirected) minimum spanning tree subgraph.