code: def test_next(self):
      for xp in (numpy, cupy):
          a = testing.shaped_arange((2, 3, 4), xp)
          e = a.flatten()
          for ai, ei in zip(a.flat, e):
              assert ai == ei
  
imports: import unittest
  import warnings
  import numpy
  import pytest
  import cupy
  from cupy import testing
label_desc: Use image node_id 3 for calling the TestFlatiter obj's underlying member method code with example usage: obj.test_next() without return types