code: def test_regressor(torch2):
      """Test regressor subclass."""
      mitigator = get_instance(
          AdversarialFairnessRegressor,
          fake_training=True,
          torch=torch2,
          tensorflow=not torch2,
      )
      assert isinstance(mitigator, _AdversarialFairness)
  
      mitigator.fit(Cont2d, Cont2d, sensitive_features=Cat)
      assert isinstance(mitigator.backendEngine_.predictor_loss, MSE)
      assert isinstance(mitigator.backendEngine_.adversary_loss, CCE)
  
imports: import sys
  import pytest
  import numpy
  import pandas
  from sklearn.utils import estimator_checks
  from fairlearn.adversarial import AdversarialFairnessClassifier, AdversarialFairnessRegressor
  from fairlearn.adversarial._adversarial_mitigation import _AdversarialFairness
  from fairlearn.adversarial._preprocessor import FloatTransformer
  from fairlearn.adversarial._constants import _TYPE_COMPLIANCE_ERROR
  from .helper import get_instance, generate_data_combinations, cols, Bin2d, Bin1d, Cat, Cont2d, Cont1d, BCE, CCE, MSE, Keyword_CATEGORY, Keyword_BINARY, Keyword_CONTINUOUS, Keyword_CLASSIFICATION, Keyword_AUTO, KeywordToClass
label_desc: Use image node_id 14 for calling a global function with example usage: test_regressor(torch2) without return types