code: def test_rsqrt():
      def rsqrt(x):
          return nd.rsqrt(x)
  
      def grad_grad_op(x):
          return 3 / (4 * nd.sqrt(x**5))
  
      sigma = random.randint(25, 100)
      mu = random.randint(500, 1000)
  
      for dim in range(1, 5):
          shape = rand_shape_nd(dim)
          array = random_arrays(shape)
          array = sigma * array + mu
          # Only positive numbers
          assert (array > 0).all()
          check_second_order_unary(array, rsqrt, grad_grad_op)
  
imports: import math
  import random
  from functools import reduce
  from operator import mul
  import random
  from common import xfail_when_nonstandard_decimal_separator
  import mxnet
  from mxnet import nd, autograd, gluon
  from mxnet.test_utils import assert_almost_equal, random_arrays, random_uniform_arrays, rand_shape_nd, same
label_desc: Use image node_id 28 for calling a global function with example usage: test_rsqrt() and returns: nd, unknown