code: def test_len(self):
      for xp in (numpy, cupy):
          a = xp.zeros((2, 3, 4))
          assert len(a.flat) == 24
          assert len(a[::2].flat) == 12
  
imports: import unittest
  import warnings
  import numpy
  import pytest
  import cupy
  from cupy import testing
label_desc: Use image node_id 4 for calling the TestFlatiter obj's underlying member method code with example usage: obj.test_len() without return types