code: def test_op_exp(operand, device_id, precision):
      e = np.exp(AA(operand, dtype=PRECISION_TO_TYPE[precision]))
      expected_forward = AA([e])
  
      expected_backward = {
          "arg": expected_forward,
      }
  
      from .. import exp
  
      _test_unary_op(
          precision,
          device_id,
          exp,
          operand,
          expected_forward,
          expected_backward,
      )
  
imports: from __future__ import division
  import numpy
  import cntk
  import pytest
  from .ops_test_utils import unittest_helper, _test_unary_op, _test_binary_op, AA, precision, PRECISION_TO_TYPE, cntk_device
  from cntk.tests.test_utils import TOLERANCE_ABSOLUTE
  from cntk.internal.utils import eval
  from cntk.internal import sanitize_dtype_cntk
  from ..None import constant
  from cntk.variables import Parameter, Constant
label_desc: Use image node_id 4 for calling a global function with example usage: test_op_exp(operand, device_id, precision) without return types