code: def test_map_dict_na_key():
      # https://github.com/pandas-dev/pandas/issues/17648
      # Checks that np.nan key is appropriately mapped
      s = Series([1, 2, np.nan])
      expected = Series(["a", "b", "c"])
      result = s.map({1: "a", 2: "b", np.nan: "c"})
      tm.assert_series_equal(result, expected)
  
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 25 for calling a global function with example usage: test_map_dict_na_key() without return types