code: def test_duplicated_nan_none(keep, expected):
      df = DataFrame(
          {"C": [np.nan, 3, 3, None, np.nan], "x": 1}, dtype=object
      )
  
      result = df.duplicated(keep=keep)
      tm.assert_series_equal(result, expected)
  
file_path: pandas/pandas/tests/frame/methods/test_duplicated.py
imports: import re
  import sys
  import numpy
  import pytest
  from pandas import DataFrame, Series, date_range
  import pandas._testing
label_desc: Use image node_id 4 for calling a global function with example usage: test_duplicated_nan_none(keep, expected) without return types