code: def test_csr(self):
      A, B = self.data()
  
      actual = _construct.vstack([A.tocsr(), B.tocsr()]).todense()
      testing.assert_array_equal(actual, self.expected())
  
imports: import functools
  import re
  from unittest import mock
  import numpy
  import pytest
  import cupy
  from cupy import testing
  from cupy.cuda import runtime
  from cupyx.scipy import sparse
  from cupyx.scipy.sparse import _construct
label_desc: Use image node_id 5 for calling the TestVstack obj's underlying member method code with example usage: obj.test_csr() without return types