code: def isolates(G):
      """Iterator over isolates in the graph.
  
      An *isolate* is a node with no neighbors (that is, with degree
      zero). For directed graphs, this means no in-neighbors and no
      out-neighbors.
  
      Parameters
      ----------
      G : NetworkX graph
  
      Returns
      -------
      iterator
          An iterator over the isolates of `G`.
  
      Examples
      --------
      To get a list of all isolates of a graph, use the :class:`list`
      constructor::
  
          >>> G = nx.Graph()
          >>> G.add_edge(1, 2)
          >>> G.add_node(3)
          >>> list(nx.isolates(G))
          [3]
  
      To remove all isolates in the graph, first create a list of the
      isolates, then use :meth:`Graph.remove_nodes_from`::
  
          >>> G.remove_nodes_from(list(nx.isolates(G)))
          >>> list(G)
          [1, 2]
  
      For digraphs, isolates have zero in-degree and zero out_degre::
  
          >>> G = nx.DiGraph([(0, 1), (1, 2)])
          >>> G.add_node(3)
          >>> list(nx.isolates(G))
          [3]
  
      """
      return (n for n, d in G.degree() if d == 0)
  
imports: import networkx
label_desc: Use image node_id 2 for calling a global function with example usage: isolates(G) and returns: unknown