code: def test_str(self):
      if numpy.dtype(self.dtype).kind == "f":
          expect = """  (1, 1)\t1.0
    (2, 2)\t2.0
    (1, 0)\t3.0
    (2, 1)\t4.0"""
      else:
          expect = """  (1, 1)\t(1+0j)
    (2, 2)\t(2+0j)
    (1, 0)\t(3+0j)
    (2, 1)\t(4+0j)"""
      assert str(self.m) == expect
  
imports: import pickle
  import unittest
  import numpy
  import pytest
  import cupy
  from cupy import testing
  from cupy.cuda import driver
  from cupy.cuda import runtime
  from cupyx.scipy import sparse
label_desc: Use image node_id 10 for calling the TestDiaMatrix obj's underlying member method code with example usage: obj.test_str() without return types