code: def test_incorrect_graph_format(self):
      data = pd.DataFrame({"X": [0], "Y": [0], "Z": [0]})
      with pytest.raises(ValueError, match="Incorrect format:"):
          model = CausalModel(
              data=data,
              treatment="Y",
              outcome="Z",
              graph=nx.Graph([("X", "Y"), ("Y", "Z")]),
          )
  
imports: import networkx
  import pandas
  import pytest
  from flaky import flaky
  from pytest import mark
  from sklearn import linear_model
  import dowhy
  import dowhy.datasets
  from dowhy import CausalModel
  from dowhy.causal_graph import CausalGraph
  from dowhy.gcm import ProbabilisticCausalModel, StructuralCausalModel
  from dowhy.utils.graph_operations import daggity_to_dot
label_desc: Use image node_id 12 for calling the TestCausalModel obj's underlying member method code with example usage: obj.test_incorrect_graph_format() without return types