code: def test_boxbox_lambda(self):
      boxcox = BoxCox(lmbda=0.3)
  
      boxcox.fit(self.multi_series)
      assert boxcox._fitted_params == [[0.3, 0.3]]
  
      boxcox = BoxCox(lmbda=[0.3, 0.4])
      boxcox.fit(self.multi_series)
      assert boxcox._fitted_params == [[0.3, 0.4]]
  
      with pytest.raises(ValueError):
          boxcox = BoxCox(lmbda=[0.2, 0.4, 0.5])
          boxcox.fit(self.multi_series)
  
      boxcox = BoxCox(optim_method="mle")
      boxcox.fit(self.multi_series)
      lmbda1 = boxcox._fitted_params[0].tolist()
  
      boxcox = BoxCox(optim_method="pearsonr")
      boxcox.fit(self.multi_series)
      lmbda2 = boxcox._fitted_params[0].tolist()
  
      assert lmbda1 != lmbda2
  
file_path: darts/darts/tests/dataprocessing/transformers/test_boxcox.py
imports: from copy import deepcopy
  import numpy
  import pandas
  import pytest
  from darts import TimeSeries
  from darts.dataprocessing.transformers import BoxCox, Mapper
  from darts.utils.timeseries_generation import linear_timeseries, sine_timeseries
label_desc: Use image node_id 1 for calling the TestBoxCox obj's underlying member method code with example usage: obj.test_boxbox_lambda() without return types