code: def test_pool_grad():
      """test cases of pool_grad"""
      verify_pool_grad(
          1, 256, 32, 3, 2, [1, 1, 1, 1], "avg", False, False
      )
      verify_pool_grad(
          1, 256, 32, 2, 2, [0, 0, 0, 0], "avg", False, True
      )
      verify_pool_grad(
          1, 256, 31, 3, 3, [1, 2, 1, 2], "avg", False, True
      )
      verify_pool_grad(
          1, 256, 32, 2, 2, [1, 2, 1, 2], "avg", False, False
      )
      verify_pool_grad(
          1, 256, 31, 4, 4, [2, 2, 2, 2], "avg", False, False
      )
      verify_pool_grad(
          1, 256, 31, 4, 4, [0, 0, 0, 0], "avg", False, False
      )
      verify_pool_grad(1, 256, 32, 2, 2, [0, 0, 0, 0], "max", False)
      verify_pool_grad(1, 256, 31, 3, 3, [2, 1, 2, 1], "max", False)
      verify_pool_grad(1, 256, 31, 3, 3, [2, 1, 2, 1], "max", True)
  
      verify_pool_grad(
          1, 256, 31, 3, 3, [2, 1, 0, 3], "avg", False, True
      )
      verify_pool_grad(
          1, 256, 32, 2, 2, [0, 3, 2, 1], "avg", False, False
      )
      verify_pool_grad(1, 256, 31, 3, 3, [1, 0, 3, 2], "max", False)
      verify_pool_grad(1, 256, 31, 3, 3, [3, 2, 1, 0], "max", True)
      verify_pool_grad(1, 256, 32, 3, 2, [1, 1, 1, 1], "max", False)
      verify_pool_grad(
          1, 256, 32, 1, 2, [1, 1, 1, 1], "avg", False, False
      )
  
      verify_pool_grad(
          1,
          256,
          31,
          4,
          4,
          [0, 0, 0, 0],
          "avg",
          False,
          False,
          add_relu=True,
      )
      verify_pool_grad(
          1, 256, 32, 2, 2, [0, 0, 0, 0], "max", False, add_relu=True
      )
  
imports: import math
  import pytest
  import numpy
  import tvm
  import tvm.testing
  import tvm.topi.testing
  from tvm import te, topi, TVMError
  from tvm.topi.utils import get_const_tuple
label_desc: Use image node_id 2 for calling a global function with example usage: test_pool_grad() without return types