code: def test_functional_sum(self):
      actual = topk(self.predictions, self.targets, 3, reduction="sum")
      self.assertEqual((), actual.shape)
      np.testing.assert_almost_equal(
          self.top_k_acc * len(self.predictions), actual, decimal=0
      )
  
imports: from unittest import TestCase, skipIf
  import numpy
  import torch
  from poutyne import Accuracy, BinaryAccuracy, TopKAccuracy, acc, bin_acc, topk
label_desc: Use image node_id 6 for calling the TopKAccuracyTest obj's underlying member method code with example usage: obj.test_functional_sum() without return types