code: def test_reduce_missing(skipna, dtype):
      arr = pd.Series([None, "a", None, "b", "c", None], dtype=dtype)
      result = arr.sum(skipna=skipna)
      if skipna:
          assert result == "abc"
      else:
          assert pd.isna(result)
  
imports: import operator
  import numpy
  import pytest
  from pandas.compat.pyarrow import pa_version_under12p0
  from pandas.core.dtypes.common import is_dtype_equal
  import pandas
  import pandas._testing
  from pandas.core.arrays.string_arrow import ArrowStringArray, ArrowStringArrayNumpySemantics
label_desc: Use image node_id 27 for calling a global function with example usage: test_reduce_missing(skipna, dtype) without return types