code: def test_setops_preserve_object_dtype(self):
      idx = Index([1, 2, 3], dtype=object)
      result = idx.intersection(idx[1:])
      expected = idx[1:]
      tm.assert_index_equal(result, expected)
  
      # if other is not monotonic increasing, intersection goes through
      #  a different route
      result = idx.intersection(idx[1:][::-1])
      tm.assert_index_equal(result, expected)
  
      result = idx._union(idx[1:], sort=None)
      expected = idx
      tm.assert_numpy_array_equal(result, expected.values)
  
      result = idx.union(idx[1:], sort=None)
      tm.assert_index_equal(result, expected)
  
      # if other is not monotonic increasing, _union goes through
      #  a different route
      result = idx._union(idx[1:][::-1], sort=None)
      tm.assert_numpy_array_equal(result, expected.values)
  
      result = idx.union(idx[1:][::-1], sort=None)
      tm.assert_index_equal(result, expected)
  
imports: from datetime import datetime
  import numpy
  import pytest
  import pandas
  from pandas import Index, Series
  import pandas._testing
  from pandas.core.algorithms import safe_sort
label_desc: Use image node_id 2 for calling the TestIndexSetOps obj's underlying member method code with example usage: obj.test_setops_preserve_object_dtype() without return types