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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def local_time_to_online(dt=None):
 """Converts datetime object to a UTC timestamp for AGOL. Args: dt (datetime):
 The :py:class:`datetime.datetime` object to convert. Defaults to ``None``, i.e., :py:func:`datetime.datetime.now`. Returns: float: A UTC timestamp as understood by AGOL (time in ms since Unix epoch * 1000) Examples: 1457167261000.0 731392515000.0 See Also: :py:func:`online_time_to_string` for converting a UTC timestamp """

    is_dst = None
    utc_offset = None
    try:
        if dt is None:
            dt = datetime.datetime.now()

        is_dst = time.daylight > 0 and time.localtime().tm_isdst > 0
        utc_offset =  (time.altzone if is_dst else time.timezone)

        return (time.mktime(dt.timetuple()) * 1000) + (utc_offset * 1000)
    except:
        line, filename, synerror = trace()
        raise ArcRestHelperError({
                    "function": "local_time_to_online",
                    "line": line,
                    "filename":  filename,
                    "synerror": synerror,
                                    }
                                    )
    finally:
        is_dst = None
        utc_offset = None

        del is_dst
        del utc_offset