code: def test_filter_using_len():
      # BUG GH4447
      df = DataFrame(
          {"A": np.arange(8), "B": list("aabbbbcc"), "C": np.arange(8)}
      )
      grouped = df.groupby("B")
      actual = grouped.filter(lambda x: len(x) > 2)
      expected = DataFrame(
          {
              "A": np.arange(2, 6),
              "B": list("bbbb"),
              "C": np.arange(2, 6),
          },
          index=np.arange(2, 6, dtype=np.int64),
      )
      tm.assert_frame_equal(actual, expected)
  
      actual = grouped.filter(lambda x: len(x) > 4)
      expected = df.loc[[]]
      tm.assert_frame_equal(actual, expected)
  
      # Series have always worked properly, but we'll test anyway.
      s = df["B"]
      grouped = s.groupby(s)
      actual = grouped.filter(lambda x: len(x) > 2)
      expected = Series(
          4 * ["b"], index=np.arange(2, 6, dtype=np.int64), name="B"
      )
      tm.assert_series_equal(actual, expected)
  
      actual = grouped.filter(lambda x: len(x) > 4)
      expected = s[[]]
      tm.assert_series_equal(actual, 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 16 for calling a global function with example usage: test_filter_using_len() without return types