docs: def normalize_timestamp(date_time):
      """
      TODO: get rid of this function and all references to it / uses of it.
      Attempt to convert a string timestamp in to a TruSTAR compatible format for submission.
      Will return current time with UTC time zone if None
      :param date_time: int that is seconds or milliseconds since epoch, or string/datetime object containing date, time,
      and (ideally) timezone.
      Examples of supported timestamp formats: 1487890914, 1487890914000, "2017-02-23T23:01:54", "2017-02-23T23:01:54+0000"
      :return If input is an int, will return milliseconds since epoch.  Otherwise, will return a normalized isoformat
      timestamp.
      """
  
      # if timestamp is null, just return the same null. 
      if not date_time:
          return date_time
  
      datetime_dt = datetime.now()
  
      # get current time in seconds-since-epoch
      current_time = int(time.time()) * 1000
  
      try:
          # identify type of timestamp and convert to datetime object
          if isinstance(date_time, int):
  
              # if timestamp has less than 10 digits, it is in seconds
              if date_time < 10000000000:
                  date_time *= 1000
  
              # if timestamp is incorrectly forward dated, set to current time
              if date_time > current_time:
                  raise ValueError("The given time %s is in the future." % date_time)
  
              return date_time
  
          if isinstance(date_time, str):
              datetime_dt = dateutil.parser.parse(date_time)
          elif isinstance(date_time, datetime):
              datetime_dt = date_time
  
      # if timestamp is none of the formats above, error message is printed and timestamp is set to current time by
      # default
      except Exception as e:
          logger.warning(e)
          logger.warning("Using current time as replacement.")
          datetime_dt = datetime.now()
  
      # if timestamp is timezone naive, add timezone
      if not datetime_dt.tzinfo:
          # add system timezone and convert to UTC
          datetime_dt = get_localzone().localize(datetime_dt).astimezone(pytz.utc)
  
      # converts datetime to iso8601
      return datetime_dt.isoformat()