code: def test_cov_raises(self):
      self.check_raises((2, 3), ddof=1.2)
      self.check_raises((3, 4, 2))
      self.check_raises((2, 3), (3, 4, 2))
  
imports: import unittest
  import numpy
  import pytest
  import cupy
  from cupy import testing
label_desc: Use image node_id 7 for calling the TestCov obj's underlying member method code with example usage: obj.test_cov_raises() without return types