code: def setup_class(cls):
      x = np.arange(400.0).reshape((100, 4))
      cls.df = pd.DataFrame(x, columns=["a", "b", "c", "d"])
      cls.series = cls.df.iloc[:, 0]
      cls.ndarray = x
  
imports: from statsmodels.compat.pandas import assert_frame_equal, assert_series_equal
  from statsmodels.compat.python import lrange
  import string
  import numpy
  from numpy.random import standard_normal
  from numpy.testing import assert_almost_equal, assert_array_equal, assert_equal, assert_string_equal
  import pandas
  import pytest
  from statsmodels.datasets import longley
  from statsmodels.tools import tools
  from statsmodels.tools.tools import pinv_extended
label_desc: Use image node_id 1 for calling the TestEnsure2d obj's underlying member method code with example usage: obj.setup_class(cls) without return types