code: def lfi_hc():
      graph = nx.Graph()
      graph.add_nodes_from([1, 2, 3, 4, 5, 6, 7, 8, 9])
      graph.add_edges_from(
          [
              (1, 2),
              (1, 5),
              (1, 6),
              (1, 7),
              (2, 3),
              (2, 8),
              (2, 9),
              (3, 4),
              (3, 8),
              (3, 9),
              (4, 5),
              (4, 6),
              (4, 7),
              (5, 6),
          ]
      )
      return graph
  
imports: import itertools
  import pytest
  import networkx
label_desc: Use image node_id 21 for calling a global function with example usage: lfi_hc() and returns: graph