code: def test_triangles_error(self):
      G = nx.diamond_graph()
      pytest.raises(nx.NetworkXError, line._triangles, G, (4, 0))
      pytest.raises(nx.NetworkXError, line._triangles, G, (0, 3))
  
imports: import pytest
  import networkx
  from networkx.generators import line
  from networkx.utils import edges_equal
label_desc: Use image node_id 1 for calling the TestGeneratorPrivateFunctions obj's underlying member method code with example usage: obj.test_triangles_error() without return types