code: def path_graph():
      """Return a path graph of length three."""
      G = nx.path_graph(3, create_using=nx.DiGraph)
      G.graph["name"] = "path"
      nx.freeze(G)
      return G
  
imports: from itertools import combinations
  import pytest
  import networkx
label_desc: Use image node_id 1 for calling a global function with example usage: path_graph() and returns: G