code: def test_converters_corner_with_nans(all_parsers):
      parser = all_parsers
      data = """id,score,days
  1,2,12
  2,2-5,
  3,,14+
  4,6-12,2"""
  
      # Example converters.
      def convert_days(x):
          x = x.strip()
  
          if not x:
              return np.nan
  
          is_plus = x.endswith("+")
  
          if is_plus:
              x = int(x[:-1]) + 1
          else:
              x = int(x)
  
          return x
  
      def convert_days_sentinel(x):
          x = x.strip()
  
          if not x:
              return np.nan
  
          is_plus = x.endswith("+")
  
          if is_plus:
              x = int(x[:-1]) + 1
          else:
              x = int(x)
  
          return x
  
      def convert_score(x):
          x = x.strip()
  
          if not x:
              return np.nan
  
          if x.find("-") > 0:
              val_min, val_max = map(int, x.split("-"))
              val = 0.5 * (val_min + val_max)
          else:
              val = float(x)
  
          return val
  
      results = []
  
      for day_converter in [convert_days, convert_days_sentinel]:
          if parser.engine == "pyarrow":
              msg = "The 'converters' option is not supported with the 'pyarrow' engine"
              with pytest.raises(ValueError, match=msg):
                  parser.read_csv(
                      StringIO(data),
                      converters={
                          "score": convert_score,
                          "days": day_converter,
                      },
                      na_values=["", None],
                  )
              continue
  
          result = parser.read_csv(
              StringIO(data),
              converters={
                  "score": convert_score,
                  "days": day_converter,
              },
              na_values=["", None],
          )
          assert pd.isna(result["days"][1])
          results.append(result)
  
      if parser.engine != "pyarrow":
          tm.assert_frame_equal(results[0], results[1])
  
file_path: pandas/pandas/tests/io/parser/test_converters.py
imports: from io import StringIO
  from dateutil.parser import parse
  import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Index
  import pandas._testing
label_desc: Use image node_id 5 for calling a global function with example usage: test_converters_corner_with_nans(all_parsers) and returns: x, x, val, np, np, np