code: def other_pser(self):
      return pd.Series([None, "z", "y", "x"], dtype="string")
  
imports: import unittest
  import numpy
  import pandas
  from pandas.api.types import CategoricalDtype
  from pyspark import pandas
  from pyspark.pandas.config import option_context
  from pyspark.testing.pandasutils import PandasOnSparkTestCase
  from pyspark.pandas.tests.data_type_ops.testing_utils import OpsTestBase
  from pyspark.pandas.typedef.typehints import extension_object_dtypes_available
label_desc: Use image node_id 3 for calling the StringExtensionOpsTest obj's underlying member method code with example usage: obj.other_pser() and returns: pd