code: def test_identify_frontdoor_functional_api(
      self,
      example_frontdoor_graph_solution: IdentificationTestFrontdoorGraphSolution,
  ):
      graph = example_frontdoor_graph_solution.graph
      expected_sets = (
          example_frontdoor_graph_solution.valid_frontdoor_sets
      )
      invalid_sets = (
          example_frontdoor_graph_solution.invalid_frontdoor_sets
      )
      frontdoor_set = identify_frontdoor(
          graph,
          observed_nodes=example_frontdoor_graph_solution.observed_nodes,
          action_nodes=["X"],
          outcome_nodes=["Y"],
      )
  
      assert (
          (len(frontdoor_set) == 0) and (len(expected_sets) == 0)
      ) or (  # No adjustments exist and that's expected.
          set(frontdoor_set) in expected_sets
          and set(frontdoor_set) not in invalid_sets
      )
  
file_path: dowhy/tests/causal_identifiers/test_frontdoor_identifier.py
imports: import numpy
  import pandas
  import pytest
  from dowhy import CausalModel
  from dowhy.causal_identifier import AutoIdentifier, BackdoorAdjustment
  from dowhy.causal_identifier.auto_identifier import identify_frontdoor
  from dowhy.causal_identifier.identify_effect import EstimandType
  from .base import IdentificationTestFrontdoorGraphSolution, example_frontdoor_graph_solution
label_desc: Use image node_id 1 for calling the TestFrontdoorIdentification obj's underlying member method code with example usage: obj.test_identify_frontdoor_functional_api(example_frontdoor_graph_solution) without return types