code: def get_field(driver, f):
      if driver in {"GPX", "GPSTrackMaker"}:
          return f["properties"]["time"]
      return f.properties["datefield"]
  
imports: import fiona
  from fiona._env import get_gdal_version_num, calc_gdal_version_num
  import pytest
  from fiona.errors import DriverSupportError
  from fiona.rfc3339 import parse_time, parse_datetime
  from .conftest import get_temp_filename
  from fiona.env import GDALVersion
  from fiona.model import Feature
  import datetime
  from fiona.drvsupport import supported_drivers, driver_mode_mingdal, _driver_converts_field_type_silently_to_str, _driver_supports_field, _driver_converts_to_str, _driver_supports_timezones, _driver_supports_milliseconds, _driver_supports_mode
  import pytz
  from pytz import timezone
label_desc: Use image node_id 4 for calling a global function with example usage: get_field(driver, f) and returns: f, f