code: def test_sum_forwarding_implementation(self):
      class MyArray(np.ndarray):
          def sum(self, axis, out):
              return "summed"
  
          def __array_function__(self, func, types, args, kwargs):
              return super().__array_function__(
                  func, types, args, kwargs
              )
  
      # note: the internal implementation of np.sum() calls the .sum() method
      array = np.array(1).view(MyArray)
      assert_equal(np.sum(array), "summed")
  
imports: import inspect
  import sys
  import os
  import tempfile
  from io import StringIO
  from unittest import mock
  import numpy
  from numpy.testing import assert_, assert_equal, assert_raises, assert_raises_regex
  from numpy.core.overrides import _get_implementing_args, array_function_dispatch, verify_matching_signatures
  from numpy.compat import pickle
  import pytest
label_desc: Use image node_id 5 for calling the TestNumPyFunctions obj's underlying member method code with example usage: obj.test_sum_forwarding_implementation() and returns: str, super