code: def setup_class(cls):
      nan = np.nan
      cls.mx_1 = np.array([[nan, 1.0], [2.0, 3.0]])
      cls.mx_2 = np.array([[nan, nan], [2.0, 3.0]])
      cls.mx_3 = np.array([[0.0, 0.0], [0.0, 0.0]])
      cls.mx_4 = np.array([[1.0, 0.0], [1.0, 0.0]])
      cls.mx_5 = np.array([[0.0, 1.0], [0.0, 1.0]])
      cls.mx_6 = np.array([[1.0, 2.0], [3.0, 4.0]])
  
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 TestNanDot obj's underlying member method code with example usage: obj.setup_class(cls) without return types