code: def test_filter_consistent_result_before_after_agg_func():
      # GH 17091
      df = DataFrame({"data": range(6), "key": list("ABCABC")})
      grouper = df.groupby("key")
      result = grouper.filter(lambda x: True)
      expected = DataFrame({"data": range(6), "key": list("ABCABC")})
      tm.assert_frame_equal(result, expected)
  
      grouper.sum()
      result = grouper.filter(lambda x: True)
      tm.assert_frame_equal(result, expected)
  
imports: from string import ascii_lowercase
  import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Series, Timestamp
  import pandas._testing
label_desc: Use image node_id 28 for calling a global function with example usage: test_filter_consistent_result_before_after_agg_func() without return types