code: def test_dummy_sparse(self):
      data = self.data
      self.grouping.dummy_sparse()
      values = data.index.get_level_values(0).values
      expected = pd.get_dummies(
          pd.Series(values, dtype="category"), drop_first=False
      )
      np.testing.assert_equal(
          self.grouping._dummies.toarray(), expected
      )
  
      if len(self.grouping.group_names) > 1:
          self.grouping.dummy_sparse(level=1)
          values = data.index.get_level_values(1).values
          expected = pd.get_dummies(
              pd.Series(values, dtype="category"), drop_first=False
          )
          np.testing.assert_equal(
              self.grouping._dummies.toarray(), expected
          )
  
imports: from statsmodels.compat.pandas import assert_frame_equal, assert_series_equal
  import numpy
  from numpy.testing import assert_equal
  import pandas
  import pytest
  from scipy import sparse
  from statsmodels.tools.grouputils import dummy_sparse, Grouping, Group, combine_indices, group_sums
  from statsmodels.datasets import grunfeld, anes96
label_desc: Use image node_id 8 for calling the CheckGrouping obj's underlying member method code with example usage: obj.test_dummy_sparse() without return types