code: def test_passthrough(passthrough):
      """Test that passthrough works as expected."""
      y = _make_series(n_columns=1)
  
      optional_passthourgh = OptionalPassthrough(
          BoxCoxTransformer(), passthrough=passthrough
      )
      box_cox = BoxCoxTransformer()
  
      y_hat_passthrough = optional_passthourgh.fit_transform(y)
      y_inv_passthrough = optional_passthourgh.inverse_transform(
          y_hat_passthrough
      )
  
      y_hat_boxcox = box_cox.fit_transform(y)
      y_inv_boxcox = box_cox.inverse_transform(y_hat_boxcox)
  
      assert_series_equal(y, y_inv_passthrough)
  
      if passthrough:
          assert_series_equal(y, y_hat_passthrough)
          with pytest.raises(AssertionError):
              assert_series_equal(y_hat_boxcox, y_hat_passthrough)
      else:
          assert_series_equal(y_hat_passthrough, y_hat_boxcox)
          assert_series_equal(y_inv_passthrough, y_inv_boxcox)
  
          with pytest.raises(AssertionError):
              assert_series_equal(y, y_hat_passthrough)
  
imports: import pytest
  from pandas.testing import assert_series_equal
  from sktime.transformations.compose import OptionalPassthrough
  from sktime.transformations.series.boxcox import BoxCoxTransformer
  from sktime.utils._testing.series import _make_series
label_desc: Use image node_id 1 for calling a global function with example usage: test_passthrough(passthrough) without return types