code: def torrents_and_ferraro_graph():
      G = nx.convert_node_labels_to_integers(
          nx.grid_graph([5, 5]), label_attribute="labels"
      )
      rlabels = nx.get_node_attributes(G, "labels")
      labels = {v: k for k, v in rlabels.items()}
  
      for nodes in [
          (labels[(0, 4)], labels[(1, 4)]),
          (labels[(3, 4)], labels[(4, 4)]),
      ]:
          new_node = G.order() + 1
          # Petersen graph is triconnected
          P = nx.petersen_graph()
          G = nx.disjoint_union(G, P)
          # Add two edges between the grid and P
          G.add_edge(new_node + 1, nodes[0])
          G.add_edge(new_node, nodes[1])
          # K5 is 4-connected
          K = nx.complete_graph(5)
          G = nx.disjoint_union(G, K)
          # Add three edges between P and K5
          G.add_edge(new_node + 2, new_node + 11)
          G.add_edge(new_node + 3, new_node + 12)
          G.add_edge(new_node + 4, new_node + 13)
          # Add another K5 sharing a node
          G = nx.disjoint_union(G, K)
          nbrs = G[new_node + 10]
          G.remove_node(new_node + 10)
          for nbr in nbrs:
              G.add_edge(new_node + 17, nbr)
          # Commenting this makes the graph not biconnected !!
          # This stupid mistake make one reviewer very angry :P
          G.add_edge(new_node + 16, new_node + 8)
  
      for nodes in [
          (labels[(0, 0)], labels[(1, 0)]),
          (labels[(3, 0)], labels[(4, 0)]),
      ]:
          new_node = G.order() + 1
          # Petersen graph is triconnected
          P = nx.petersen_graph()
          G = nx.disjoint_union(G, P)
          # Add two edges between the grid and P
          G.add_edge(new_node + 1, nodes[0])
          G.add_edge(new_node, nodes[1])
          # K5 is 4-connected
          K = nx.complete_graph(5)
          G = nx.disjoint_union(G, K)
          # Add three edges between P and K5
          G.add_edge(new_node + 2, new_node + 11)
          G.add_edge(new_node + 3, new_node + 12)
          G.add_edge(new_node + 4, new_node + 13)
          # Add another K5 sharing two nodes
          G = nx.disjoint_union(G, K)
          nbrs = G[new_node + 10]
          G.remove_node(new_node + 10)
          for nbr in nbrs:
              G.add_edge(new_node + 17, nbr)
          nbrs2 = G[new_node + 9]
          G.remove_node(new_node + 9)
          for nbr in nbrs2:
              G.add_edge(new_node + 18, nbr)
      return G
  
imports: import itertools
  import pytest
  import networkx
  from networkx.algorithms import flow
  from networkx.algorithms.connectivity.kcutsets import _is_separating_set
label_desc: Use image node_id 2 for calling a global function with example usage: torrents_and_ferraro_graph() and returns: G