code: def test_split_to_dataframe_unequal_splits(any_string_dtype):
      s = Series(
          ["some_unequal_splits", "one_of_these_things_is_not"],
          dtype=any_string_dtype,
      )
      result = s.str.split("_", expand=True)
      exp = DataFrame(
          {
              0: ["some", "one"],
              1: ["unequal", "of"],
              2: ["splits", "these"],
              3: [None, "things"],
              4: [None, "is"],
              5: [None, "not"],
          },
          dtype=any_string_dtype,
      )
      tm.assert_frame_equal(result, exp)
  
imports: from datetime import datetime
  import re
  import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Index, MultiIndex, Series, _testing
  from pandas.tests.strings import _convert_na_value, object_pyarrow_numpy
label_desc: Use image node_id 17 for calling a global function with example usage: test_split_to_dataframe_unequal_splits(any_string_dtype) without return types