code: def test_union_sort_other_empty(slice_):
      # https://github.com/pandas-dev/pandas/issues/24959
      idx = MultiIndex.from_product([[1, 0], ["a", "b"]])
  
      # default, sort=None
      other = idx[slice_]
      tm.assert_index_equal(idx.union(other), idx)
      tm.assert_index_equal(other.union(idx), idx)
  
      # sort=False
      tm.assert_index_equal(idx.union(other, sort=False), idx)
  
imports: import numpy
  import pytest
  import pandas
  from pandas import CategoricalIndex, DataFrame, Index, IntervalIndex, MultiIndex, Series
  import pandas._testing
  from pandas.api.types import is_float_dtype, is_unsigned_integer_dtype
label_desc: Use image node_id 20 for calling a global function with example usage: test_union_sort_other_empty(slice_) without return types