code: def test_union_with_missing_values_on_both_sides(nulls_fixture):
      # GH#38623
      mi1 = MultiIndex.from_arrays([[1, nulls_fixture]])
      mi2 = MultiIndex.from_arrays([[1, nulls_fixture, 3]])
      result = mi1.union(mi2)
      expected = MultiIndex.from_arrays([[1, 3, nulls_fixture]])
      tm.assert_index_equal(result, expected)
  
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 35 for calling a global function with example usage: test_union_with_missing_values_on_both_sides(nulls_fixture) without return types