docs: def timezone(zone):
      """Try to get timezone using pytz or python-dateutil
  
      :param zone: timezone str
      :return: timezone tzinfo or None
      """
      try:
          import pytz
          return pytz.timezone(zone)
      except ImportError:
          pass
      try:
          from dateutil.tz import gettz
          return gettz(zone)
      except ImportError:
          return None