code: def test_lowess_regression(self):
      p = lm._RegressionPlotter("x", "y", data=self.df, lowess=True)
      grid, yhat, err_bands = p.fit_regression(x_range=(-3, 3))
  
      assert len(grid) == len(yhat)
      assert err_bands is None
  
imports: import warnings
  import numpy
  import matplotlib
  import matplotlib.pyplot
  import pandas
  import pytest
  import numpy.testing
  import pandas.testing
  from seaborn import regression
  from seaborn.palettes import color_palette
label_desc: Use image node_id 26 for calling the TestRegressionPlotter obj's underlying member method code with example usage: obj.test_lowess_regression() without return types