code: def poke(ser, per=0.05):
      s = ser.copy()
      for _ in range(int(per * len(ser))):
          s.iloc[np.random.randint(len(ser))] = np.nan
      return s
  
imports: import pytest
  from tests.unit.profile.base import *
  from tslumen.profile.features import ft_stl, ft_entropy, ft_acf, ft_pacf, ft_tilewin, ft_cross_pts, ft_kpss, ft_adfuller
label_desc: Use image node_id 2 for calling a global function with example usage: poke(ser, per) and returns: s