code: def test_spilt_join_roundtrip_mixed_object():
      ser = Series(
          [
              "a_b",
              np.nan,
              "asdf_cas_asdf",
              True,
              datetime.today(),
              "foo",
              None,
              1,
              2.0,
          ]
      )
      result = ser.str.split("_").str.join("_")
      expected = Series(
          [
              "a_b",
              np.nan,
              "asdf_cas_asdf",
              np.nan,
              np.nan,
              "foo",
              None,
              np.nan,
              np.nan,
          ],
          dtype=object,
      )
      tm.assert_series_equal(result, expected)
  
imports: from datetime import datetime, timedelta
  import numpy
  import pytest
  from pandas import DataFrame, Index, MultiIndex, Series
  import pandas._testing
  from pandas.core.strings.accessor import StringMethods
  from pandas.tests.strings import object_pyarrow_numpy
label_desc: Use image node_id 13 for calling a global function with example usage: test_spilt_join_roundtrip_mixed_object() without return types