def METHOD_NAME(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)