code: def check_invalid_option(self, xp):
      a = xp.asarray(self.a)
      p = xp.asarray(self.p)
      n = xp.asarray(self.n)
  
      with self.assertRaises(ValueError):
          functions.triplet(a, p, n, reduce="invalid_option")
  
imports: import unittest
  import numpy
  import six
  import chainer
  from chainer.backends import cuda
  from chainer import functions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 2 for calling the TestContrastiveInvalidReductionOption obj's underlying member method code with example usage: obj.check_invalid_option(xp) without return types