code: def test_map_decimal(string_series):
      result = string_series.map(lambda x: Decimal(str(x)))
      assert result.dtype == np.object_
      assert isinstance(result.iloc[0], Decimal)
  
imports: from collections import Counter, defaultdict
  from decimal import Decimal
  import math
  import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Index, MultiIndex, Series, bdate_range, date_range, isna, timedelta_range
  import pandas._testing
label_desc: Use image node_id 20 for calling a global function with example usage: test_map_decimal(string_series) without return types