code: def test_astype_preserves_subclass(self):
      # GH#40810
      df = tm.SubclassedDataFrame(
          {"A": [1, 2, 3], "B": [4, 5, 6], "C": [7, 8, 9]}
      )
  
      result = df.astype(
          {"A": np.int64, "B": np.int32, "C": np.float64}
      )
      assert isinstance(result, tm.SubclassedDataFrame)
  
imports: import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Index, MultiIndex, Series
  import pandas._testing
label_desc: Use image node_id 31 for calling the TestDataFrameSubclassing obj's underlying member method code with example usage: obj.test_astype_preserves_subclass() without return types