code: def lf_shc():
      graph = nx.Graph()
      graph.add_nodes_from([1, 2, 3, 4, 5, 6])
      graph.add_edges_from([(6, 1), (1, 4), (4, 3), (3, 2), (2, 5)])
      return graph
  
imports: import itertools
  import pytest
  import networkx
label_desc: Use image node_id 12 for calling a global function with example usage: lf_shc() and returns: graph