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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 format_delta(__timedelta: datetime.timedelta) -> str: """Format ISO-8601 duration string. Args: __timedelta: Duration to process Returns: ISO-8601 representation of duration """

    if __timedelta == datetime.timedelta(0):
        return ''
    days_s = '{}D'.format(__timedelta.days) if __timedelta.days else ''
    hours, minutes = divmod(__timedelta.seconds, 3600)
    minutes, seconds = divmod(minutes, 60)
    hours_s = '{:02d}H'.format(hours) if hours else ''
    minutes_s = '{:02d}M'.format(minutes) if minutes else ''
    seconds_s = '{:02d}S'.format(seconds) if seconds else ''
    return 'P{}{}{}{}{}'.format(days_s,
                                'T' if hours or minutes or seconds else '',
                                hours_s, minutes_s, seconds_s)