code: def test_series_transform_batch(self):
      pdf, psdf = self.df_pair
  
      self.assert_eq(
          psdf.a.pandas_on_spark.transform_batch(
              lambda pser: pser.astype(str)
          ).sort_index(),
          pdf.a.astype(str).sort_index(),
      )
  
      pdf = pd.DataFrame(
          {
              "a": ["a", "b", "c", "a", "b", "c"],
              "b": ["b", "a", "c", "c", "b", "a"],
          }
      )
      psdf = ps.from_pandas(pdf)
  
      dtype = CategoricalDtype(categories=["a", "b", "c", "d"])
  
      self.assert_eq(
          psdf.a.pandas_on_spark.transform_batch(
              lambda pser: pser.astype(dtype)
          ).sort_index(),
          pdf.a.astype(dtype).sort_index(),
      )
  
imports: import numpy
  import pandas
  from pandas.api.types import CategoricalDtype
  import pyspark.pandas
  from pyspark.testing.pandasutils import ComparisonTestBase, TestUtils
label_desc: Use image node_id 27 for calling the CategoricalTestsMixin obj's underlying member method code with example usage: obj.test_series_transform_batch() without return types