code: def test_qcut_nas():
      arr = np.random.default_rng(2).standard_normal(100)
      arr[:20] = np.nan
  
      result = qcut(arr, 4)
      assert isna(result[:20]).all()
  
imports: import os
  import numpy
  import pytest
  import pandas
  from pandas import Categorical, DatetimeIndex, Interval, IntervalIndex, NaT, Series, Timedelta, TimedeltaIndex, Timestamp, cut, date_range, isna, qcut, timedelta_range
  import pandas._testing
  from pandas.api.types import CategoricalDtype
  from pandas.tseries.offsets import Day
label_desc: Use image node_id 6 for calling a global function with example usage: test_qcut_nas() without return types