code: def test_astype(self):
      pser = pd.Series(["a", "b", "c"])
      psser = ps.from_pandas(pser)
  
      self.assert_eq(psser.astype("category"), pser.astype("category"))
      self.assert_eq(
          psser.astype(CategoricalDtype(["c", "a", "b"])),
          pser.astype(CategoricalDtype(["c", "a", "b"])),
      )
  
      pcser = pser.astype(CategoricalDtype(["c", "a", "b"]))
      pscser = psser.astype(CategoricalDtype(["c", "a", "b"]))
  
      self.assert_eq(
          pscser.astype("category"), pcser.astype("category")
      )
  
      self.assert_eq(
          pscser.astype(CategoricalDtype(["b", "c", "a"])),
          pcser.astype(CategoricalDtype(["b", "c", "a"])),
      )
  
      self.assert_eq(pscser.astype(str), pcser.astype(str))
  
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 11 for calling the CategoricalTestsMixin obj's underlying member method code with example usage: obj.test_astype() without return types