code: def _ndtr(a: np.ndarray) -> np.ndarray:
      # todo(amylase): implement erfc in _erf.py and use it for big |a| inputs.
      return 0.5 + 0.5 * erf(a / 2**0.5)
  
imports: import functools
  import math
  import sys
  from typing import Callable
  from typing import Optional
  from typing import Union
  import numpy
  from optuna.samplers._tpe._erf import erf
label_desc: Use image node_id 4 for calling a global function with example usage: _ndtr(a) and returns: unknown