code: def test_methods(self, method, expected_data):
      # GH 16037
      df = DataFrame({"A": ["a"] * 4, "B": range(4)})
      result = getattr(df.groupby("A").ewm(com=1.0), method)()
      expected = DataFrame(
          {"B": expected_data},
          index=MultiIndex.from_tuples(
              [
                  ("a", 0),
                  ("a", 1),
                  ("a", 2),
                  ("a", 3),
              ],
              names=["A", None],
          ),
      )
      tm.assert_frame_equal(result, expected)
  
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 1 for calling the TestEWM obj's underlying member method code with example usage: obj.test_methods(method, expected_data) without return types