code: def setup_class(cls):
      nobs, k_vars = 100, 4
      x = np.random.randn(nobs, k_vars)
      x[:, 0] = 1
      y = x[:, :-1].sum(1) + np.random.randn(nobs)
      cls.res = OLS(y, x).fit()
  
file_path: statsmodels/statsmodels/stats/tests/test_deltacov.py
imports: import numpy
  from numpy.testing import assert_allclose, assert_equal
  from statsmodels.regression.linear_model import OLS
  from statsmodels.stats._delta_method import NonlinearDeltaCov
label_desc: Use image node_id 1 for calling the TestDeltacovOLS obj's underlying member method code with example usage: obj.setup_class(cls) without return types