code: def test_prevent_casting(self, simple_index):
      index = simple_index
      result = index.astype("O")
      assert result.dtype == np.object_
  
imports: import numpy
  import pytest
  import pandas
  from pandas import Index, Series
  import pandas._testing
label_desc: Use image node_id 9 for calling the TestNumericInt obj's underlying member method code with example usage: obj.test_prevent_casting(simple_index) without return types