code: def test_nullify():
      series = pd.Series([1, 3, 5, 7, 166])
      expected_nan_count = 3
      new_series = nullify(col=series, perc=0.6)
      new_nan_count = sum(new_series.isna())
      assert expected_nan_count == new_nan_count
  
file_path: fklearn/tests/validation/test_perturbators.py
imports: from fklearn.validation.perturbators import shift_mu, random_noise, nullify, sample_columns, perturbator
  import pandas
  import numpy
label_desc: Use image node_id 3 for calling a global function with example usage: test_nullify() without return types