code: def test_precise_conversion(c_parser_only, num):
      parser = c_parser_only
  
      normal_errors = []
      precise_errors = []
  
      def error(val: float, actual_val: Decimal) -> Decimal:
          return abs(Decimal(f"{val:.100}") - actual_val)
  
      # 25 decimal digits of precision
      text = f"a\n{num:.25}"
  
      normal_val = float(
          parser.read_csv(StringIO(text), float_precision="legacy")[
              "a"
          ][0]
      )
      precise_val = float(
          parser.read_csv(StringIO(text), float_precision="high")["a"][
              0
          ]
      )
      roundtrip_val = float(
          parser.read_csv(StringIO(text), float_precision="round_trip")[
              "a"
          ][0]
      )
      actual_val = Decimal(text[2:])
  
      normal_errors.append(error(normal_val, actual_val))
      precise_errors.append(error(precise_val, actual_val))
  
      # round-trip should match float()
      assert roundtrip_val == float(text[2:])
  
      assert sum(precise_errors) <= sum(normal_errors)
      assert max(precise_errors) <= max(normal_errors)
  
imports: from decimal import Decimal
  from io import BytesIO, StringIO, TextIOWrapper
  import mmap
  import os
  import tarfile
  import numpy
  import pytest
  from pandas.compat.numpy import np_version_gte1p24
  from pandas.errors import ParserError, ParserWarning
  import pandas.util._test_decorators
  from pandas import DataFrame, concat
  import pandas._testing
label_desc: Use image node_id 5 for calling a global function with example usage: test_precise_conversion(c_parser_only, num) and returns: abs