code: def test_cov_warns(self):
      self.check_warns((2, 3), ddof=3)
      self.check_warns((2, 3), ddof=4)
  
imports: import unittest
  import numpy
  import pytest
  import cupy
  from cupy import testing
label_desc: Use image node_id 6 for calling the TestCov obj's underlying member method code with example usage: obj.test_cov_warns() without return types