code: def test_filter_nan_is_false():
      df = DataFrame(
          {"A": np.arange(8), "B": list("aabbbbcc"), "C": np.arange(8)}
      )
      s = df["B"]
      g_df = df.groupby(df["B"])
      g_s = s.groupby(s)
  
      f = lambda x: np.nan
      tm.assert_frame_equal(g_df.filter(f), df.loc[[]])
      tm.assert_series_equal(g_s.filter(f), s[[]])
  
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 11 for calling a global function with example usage: test_filter_nan_is_false() without return types