code: def test_cov(self):
      pser1 = pd.Series(
          [0.90010907, 0.13484424, 0.62036035], index=[0, 1, 2]
      )
      pser2 = pd.Series(
          [0.12528585, 0.26962463, 0.51111198], index=[1, 2, 3]
      )
      self._test_cov(pser1, pser2)
  
      pser1 = pd.Series(
          [0.90010907, 0.13484424, 0.62036035], index=[0, 1, 2]
      )
      pser2 = pd.Series(
          [0.12528585, 0.26962463, 0.51111198, 0.32076008],
          index=[1, 2, 3, 4],
      )
      self._test_cov(pser1, pser2)
  
      pser1 = pd.Series(
          [0.90010907, 0.13484424, 0.62036035, 0.32076008],
          index=[0, 1, 2, 3],
      )
      pser2 = pd.Series([0.12528585, 0.26962463], index=[1, 2])
      self._test_cov(pser1, pser2)
  
      psser1 = ps.from_pandas(pser1)
      with self.assertRaisesRegex(
          TypeError, "unsupported type: <class 'list'>"
      ):
          psser1.cov([0.12528585, 0.26962463, 0.51111198])
      with self.assertRaisesRegex(
          TypeError,
          "unsupported type: <class 'pandas.core.series.Series'>",
      ):
          psser1.cov(pser2)
  
file_path: spark/python/pyspark/pandas/tests/diff_frames_ops/test_cov.py
imports: import pandas
  from pyspark import pandas
  from pyspark.pandas.config import set_option, reset_option
  from pyspark.testing.pandasutils import PandasOnSparkTestCase
  from pyspark.testing.sqlutils import SQLTestUtils
label_desc: Use image node_id 3 for calling the DiffFramesCovMixin obj's underlying member method code with example usage: obj.test_cov() without return types