code: def test_regression_limits(self):
      f, ax = plt.subplots()
      ax.scatter(self.df.x, self.df.y)
      p = lm._RegressionPlotter("x", "y", data=self.df)
      grid, _, _ = p.fit_regression(ax)
      xlim = ax.get_xlim()
      assert grid.min() == xlim[0]
      assert grid.max() == xlim[1]
  
      p = lm._RegressionPlotter("x", "y", data=self.df, truncate=True)
      grid, _, _ = p.fit_regression()
      assert grid.min() == self.df.x.min()
      assert grid.max() == self.df.x.max()
  
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 28 for calling the TestRegressionPlotter obj's underlying member method code with example usage: obj.test_regression_limits() without return types