code: def test_dummies_groups(self):
      # calls dummy_sparse under the hood
      self.grouping.dummies_groups()
  
      if len(self.grouping.group_names) > 1:
          self.grouping.dummies_groups(level=1)
  
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 7 for calling the CheckGrouping obj's underlying member method code with example usage: obj.test_dummies_groups() without return types