code: def test_groupby_dataframe_slice_then_transform(dropna, index):
      # GH35014 & GH35612
      expected_data = {"B": [2, 2, 1, np.nan if dropna else 1]}
  
      df = pd.DataFrame(
          {"A": [0, 0, 1, None], "B": [1, 2, 3, None]}, index=index
      )
      gb = df.groupby("A", dropna=dropna)
  
      result = gb.transform(len)
      expected = pd.DataFrame(expected_data, index=index)
      tm.assert_frame_equal(result, expected)
  
      result = gb[["B"]].transform(len)
      expected = pd.DataFrame(expected_data, index=index)
      tm.assert_frame_equal(result, expected)
  
      result = gb["B"].transform(len)
      expected = pd.Series(expected_data["B"], index=index, name="B")
      tm.assert_series_equal(result, expected)
  
imports: import numpy
  import pytest
  from pandas.compat.pyarrow import pa_version_under10p1
  from pandas.core.dtypes.missing import na_value_for_dtype
  import pandas
  import pandas._testing
  from pandas.tests.groupby import get_groupby_method_args
label_desc: Use image node_id 7 for calling a global function with example usage: test_groupby_dataframe_slice_then_transform(dropna, index) without return types