How to use the aniso8601.date.parse_date function in aniso8601

def _parse_duration_combined(durationstr, relative):
    #Period of the form PT<time>

    #Split the string in to its component parts
    datepart, timepart = durationstr[1:].split('T') #We skip the 'P'

    datevalue = parse_date(datepart)
    timevalue = parse_time(timepart)

    if relative is True:
        return dateutil.relativedelta.relativedelta(years=datevalue.year, months=datevalue.month, days=datevalue.day, hours=timevalue.hour, minutes=timevalue.minute, seconds=timevalue.second, microseconds=timevalue.microsecond)
    else:
        totaldays = datevalue.year * 365 + datevalue.month * 30 + datevalue.day

        return datetime.timedelta(days=totaldays, hours=timevalue.hour, minutes=timevalue.minute, seconds=timevalue.second, microseconds=timevalue.microsecond)
</time>

def parse_datetime(isodatetimestr, delimiter='T'):
    #Given a string in ISO 8601 date time format, return a datetime.datetime
    #object that corresponds to the given date time.
    #By default, the ISO 8601 specified T delimiter is used to split the
    #date and time (T<time>). Fixed offset tzdata will be included
    #if UTC offset is given in the input string.

    isodatestr, isotimestr = isodatetimestr.split(delimiter)

    datepart = parse_date(isodatestr)
    timepart = parse_time(isotimestr)

    return datetime.datetime.combine(datepart, timepart)
</time>

#See if we need to upconvert to datetime to preserve resolution
            if secondpart.find(datetimedelimiter) != -1:
                return (startdate, datetime.combine(startdate, datetime.min.time()) + duration)
            else:
                return (startdate, startdate + duration)
    else:
        #/
        if firstpart.find(datetimedelimiter) != -1 and secondpart.find(datetimedelimiter) != -1:
            #Both parts are datetimes
            return (parse_datetime(firstpart, delimiter=datetimedelimiter), parse_datetime(secondpart, delimiter=datetimedelimiter))
        elif firstpart.find(datetimedelimiter) != -1 and secondpart.find(datetimedelimiter) == -1:
            #First part is a datetime, second part is a date
            return (parse_datetime(firstpart, delimiter=datetimedelimiter), parse_date(secondpart))
        elif firstpart.find(datetimedelimiter) == -1 and secondpart.find(datetimedelimiter) != -1:
            #First part is a date, second part is a datetime
            return (parse_date(firstpart), parse_datetime(secondpart, delimiter=datetimedelimiter))
        else:
            #Both parts are dates
            return (parse_date(firstpart), parse_date(secondpart))

return (enddate, datetime.combine(enddate, datetime.min.time()) - duration)
            else:
                return (enddate, enddate - duration)
    elif secondpart[0] == 'P':
        #/
        #We need to figure out if  is a date, or a datetime
        if firstpart.find(datetimedelimiter) != -1:
            # is a datetime
            duration = parse_duration(secondpart, relative=relative)
            startdatetime = parse_datetime(firstpart, delimiter=datetimedelimiter)

            return (startdatetime, startdatetime + duration)
        else:
            # must just be a date
            duration = parse_duration(secondpart, relative=relative)
            startdate = parse_date(firstpart)

            #See if we need to upconvert to datetime to preserve resolution
            if secondpart.find(datetimedelimiter) != -1:
                return (startdate, datetime.combine(startdate, datetime.min.time()) + duration)
            else:
                return (startdate, startdate + duration)
    else:
        #/
        if firstpart.find(datetimedelimiter) != -1 and secondpart.find(datetimedelimiter) != -1:
            #Both parts are datetimes
            return (parse_datetime(firstpart, delimiter=datetimedelimiter), parse_datetime(secondpart, delimiter=datetimedelimiter))
        elif firstpart.find(datetimedelimiter) != -1 and secondpart.find(datetimedelimiter) == -1:
            #First part is a datetime, second part is a date
            return (parse_datetime(firstpart, delimiter=datetimedelimiter), parse_date(secondpart))
        elif firstpart.find(datetimedelimiter) == -1 and secondpart.find(datetimedelimiter) != -1:
            #First part is a date, second part is a datetime

else:
                return (startdate, startdate + duration)
    else:
        #/
        if firstpart.find(datetimedelimiter) != -1 and secondpart.find(datetimedelimiter) != -1:
            #Both parts are datetimes
            return (parse_datetime(firstpart, delimiter=datetimedelimiter), parse_datetime(secondpart, delimiter=datetimedelimiter))
        elif firstpart.find(datetimedelimiter) != -1 and secondpart.find(datetimedelimiter) == -1:
            #First part is a datetime, second part is a date
            return (parse_datetime(firstpart, delimiter=datetimedelimiter), parse_date(secondpart))
        elif firstpart.find(datetimedelimiter) == -1 and secondpart.find(datetimedelimiter) != -1:
            #First part is a date, second part is a datetime
            return (parse_date(firstpart), parse_datetime(secondpart, delimiter=datetimedelimiter))
        else:
            #Both parts are dates
            return (parse_date(firstpart), parse_date(secondpart))

#Notice that these are not returned 'in order' (earlier to later), this
        #is to maintain consistency with parsing / durations, as
        #well as making repeating interval code cleaner. Users who desire
        #durations to be in order can use the 'sorted' operator.

        #We need to figure out if  is a date, or a datetime
        if secondpart.find(datetimedelimiter) != -1:
            # is a datetime
            duration = parse_duration(firstpart, relative=relative)
            enddatetime = parse_datetime(secondpart, delimiter=datetimedelimiter)

            return (enddatetime, enddatetime - duration)
        else:
            # must just be a date
            duration = parse_duration(firstpart, relative=relative)
            enddate = parse_date(secondpart)

            #See if we need to upconvert to datetime to preserve resolution
            if firstpart.find(datetimedelimiter) != -1:
                return (enddate, datetime.combine(enddate, datetime.min.time()) - duration)
            else:
                return (enddate, enddate - duration)
    elif secondpart[0] == 'P':
        #/
        #We need to figure out if  is a date, or a datetime
        if firstpart.find(datetimedelimiter) != -1:
            # is a datetime
            duration = parse_duration(secondpart, relative=relative)
            startdatetime = parse_datetime(firstpart, delimiter=datetimedelimiter)

            return (startdatetime, startdatetime + duration)
        else: