code: def test_sort_index_reorder_on_ops(self):
      # GH#15687
      df = DataFrame(
          np.random.default_rng(2).standard_normal((8, 2)),
          index=MultiIndex.from_product(
              [["a", "b"], ["big", "small"], ["red", "blu"]],
              names=["letter", "size", "color"],
          ),
          columns=["near", "far"],
      )
      df = df.sort_index()
  
      def my_func(group):
          group.index = ["newz", "newa"]
          return group
  
      result = (
          df.groupby(level=["letter", "size"])
          .apply(my_func)
          .sort_index()
      )
      expected = MultiIndex.from_product(
          [["a", "b"], ["big", "small"], ["newa", "newz"]],
          names=["letter", "size", None],
      )
  
      tm.assert_index_equal(result.index, expected)
  
imports: import numpy
  import pytest
  import pandas
  from pandas import CategoricalDtype, CategoricalIndex, DataFrame, IntervalIndex, MultiIndex, RangeIndex, Series, Timestamp
  import pandas._testing
label_desc: Use image node_id 3 for calling the TestDataFrameSortIndex obj's underlying member method code with example usage: obj.test_sort_index_reorder_on_ops() and returns: group