docs: def localize(dt, force_to_local=True):
    """Localize a datetime to the local timezone.
  
    If dt is naive, returns the same datetime with the local timezone, otherwise
    uses astimezone to convert.
  
    Args:
      dt: datetime object.
      force_to_local: Force all results to be in local time.
  
    Returns:
      A datetime_tz object.
    """
    if not isinstance(dt, datetime_tz):
      if not dt.tzinfo:
        return datetime_tz(dt, tzinfo=localtz())
      dt = datetime_tz(dt)
    if force_to_local:
      return dt.astimezone(localtz())
    return dt