[python] In Python, how do you convert a `datetime` object to seconds?

I tried the standard library's calendar.timegm and it works quite well:

# convert a datetime to milliseconds since Epoch
def datetime_to_utc_milliseconds(aDateTime):
    return int(calendar.timegm(aDateTime.timetuple())*1000)

Ref: https://docs.python.org/2/library/calendar.html#calendar.timegm