code: def test_diamond_graph(self):
      G = nx.diamond_graph()
      for edge in G.edges:
          cell = line._select_starting_cell(G, starting_edge=edge)
          # Starting cell should always be one of the two triangles
          assert len(cell) == 3
          assert all(v in G[u] for u in cell for v in cell if u != v)
  
imports: import pytest
  import networkx
  from networkx.generators import line
  from networkx.utils import edges_equal
label_desc: Use image node_id 4 for calling the TestGeneratorPrivateFunctions obj's underlying member method code with example usage: obj.test_diamond_graph() without return types