code: def test_pandas(self):
      results = tools._ensure_2d(self.df, False)
      assert_frame_equal(results[0], self.df)
      assert_array_equal(results[1], self.df.columns)
  
      results = tools._ensure_2d(self.series, False)
      assert_frame_equal(results[0], self.df.iloc[:, [0]])
      assert_equal(results[1], self.df.columns[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 3 for calling the TestEnsure2d obj's underlying member method code with example usage: obj.test_pandas() without return types