code: def test_union_categoricals_empty(
      self, val, request, using_infer_string
  ):
      # GH 13759
      if using_infer_string and val == ["1"]:
          request.applymarker(
              pytest.mark.xfail("object and strings dont match")
          )
      res = union_categoricals([Categorical([]), Categorical(val)])
      exp = Categorical(val)
      tm.assert_categorical_equal(res, exp)
  
imports: import numpy
  import pytest
  from pandas.core.dtypes.concat import union_categoricals
  import pandas
  from pandas import Categorical, CategoricalIndex, Series
  import pandas._testing
label_desc: Use image node_id 7 for calling the TestUnionCategoricals obj's underlying member method code with example usage: obj.test_union_categoricals_empty(val, request, using_infer_string) without return types