code: def test_dont_mutate_obj_after_slicing(self):
      # GH 43355
      df = DataFrame(
          {
              "id": ["a", "a", "b", "b", "b"],
              "timestamp": date_range("2021-9-1", periods=5, freq="h"),
              "y": range(5),
          }
      )
      grp = df.groupby("id").rolling("1h", on="timestamp")
      result = grp.count()
      expected_df = DataFrame(
          {
              "timestamp": date_range("2021-9-1", periods=5, freq="h"),
              "y": [1.0] * 5,
          },
          index=MultiIndex.from_arrays(
              [["a", "a", "b", "b", "b"], list(range(5))],
              names=["id", None],
          ),
      )
      tm.assert_frame_equal(result, expected_df)
  
      result = grp["y"].count()
      expected_series = Series(
          [1.0] * 5,
          index=MultiIndex.from_arrays(
              [
                  ["a", "a", "b", "b", "b"],
                  date_range("2021-9-1", periods=5, freq="h"),
              ],
              names=["id", "timestamp"],
          ),
          name="y",
      )
      tm.assert_series_equal(result, expected_series)
      # This is the key test
      result = grp.count()
      tm.assert_frame_equal(result, expected_df)
  
imports: import numpy
  import pytest
  from pandas import DataFrame, DatetimeIndex, Index, MultiIndex, Series, Timestamp, date_range, to_datetime
  import pandas._testing
  from pandas.api.indexers import BaseIndexer
  from pandas.core.groupby.groupby import get_groupby
label_desc: Use image node_id 5 for calling the TestEWM obj's underlying member method code with example usage: obj.test_dont_mutate_obj_after_slicing() without return types