code: def test_valid_guerrero(self):
      # `l <- BoxCox.lambda(x, method="guerrero")` on a ts object
      # with frequency 4 (BoxCox.lambda defaults to 2, but we use
      # Guerrero and Perera (2004) as a guideline)
      lmbda = self.bc._est_lambda(
          self.x, method="guerrero", window_length=4
      )
      assert_almost_equal(lmbda, 0.507624, 4)
  
      # `l <- BoxCox.lambda(x, method="guerrero")` with the default grouping
      # parameter (namely, window_length=2).
      lmbda = self.bc._est_lambda(
          self.x, method="guerrero", window_length=2
      )
      assert_almost_equal(lmbda, 0.513893, 4)
  
file_path: statsmodels/statsmodels/base/tests/test_transform.py
imports: import numpy
  from numpy.testing import assert_almost_equal, assert_equal, assert_raises
  from statsmodels.base.transform import BoxCox
  from statsmodels.datasets import macrodata
label_desc: Use image node_id 6 for calling the TestTransform obj's underlying member method code with example usage: obj.test_valid_guerrero() without return types