docs: def to_networkx(self, directed=None):
      '''Converts this Graph object to a networkx-compatible object.
      Requires the networkx library.'''
      import networkx as nx
      directed = directed if directed is not None else self.is_directed()
      cls = nx.DiGraph if directed else nx.Graph
      adj = self.matrix()
      if ss.issparse(adj):
        return nx.from_scipy_sparse_matrix(adj, create_using=cls())
      return nx.from_numpy_matrix(adj, create_using=cls())