code: def _ndtr_cpu(x, dtype):
      erfc = numpy.vectorize(lambda x: 0.5 * math.erfc(-x / 2**0.5))
      return utils.force_array(erfc(x), dtype=dtype)
  
file_path: chainer/tests/chainer_tests/functions_tests/math_tests/test_ndtr.py
imports: import math
  import unittest
  import numpy
  from chainer import backend
  from chainer.backends import cuda
  import chainer.functions
  from chainer import testing
  from chainer import utils
label_desc: Use image node_id 1 for calling a global function with example usage: _ndtr_cpu(x, dtype) and returns: utils