code: def setup_class(cls):
      np.random.seed(654123)
  
      # generate an interesting dataset with heteroscedasticity
      nobs = 200
      x = np.random.uniform(-4, 4, nobs)
      y = mean_func(x) + std_func(x) * np.random.randn(nobs)
  
      cls.df = pd.DataFrame({"temp": x, "dens": y})
  
file_path: statsmodels/statsmodels/robust/tests/test_mquantiles.py
imports: import numpy
  from numpy.testing import assert_allclose
  import pandas
  from statsmodels.regression.linear_model import OLS
  from statsmodels.regression.quantile_regression import QuantReg
  from statsmodels.robust import norms
  from statsmodels.robust.robust_linear_model import RLM
label_desc: Use image node_id 1 for calling the TestMQuantiles obj's underlying member method code with example usage: obj.setup_class(cls) without return types