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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 _pretty_time_delta(td):
 """Creates a string representation of a time delta. Parameters td : :class:`datetime.timedelta` Returns ------- pretty_formatted_datetime : str """

    seconds = td.total_seconds()
    sign_string = '-' if seconds < 0 else ''
    seconds = abs(int(seconds))
    days, seconds = divmod(seconds, 86400)
    hours, seconds = divmod(seconds, 3600)
    minutes, seconds = divmod(seconds, 60)
    d = dict(sign=sign_string, days=days, hours=hours, minutes=minutes, seconds=seconds)
    if days > 0:
        return '{sign}{days}d{hours:02d}h{minutes:02d}m:{seconds:02d}s'.format(**d)
    elif hours > 0:
        return '{sign}{hours:02d}h{minutes:02d}m:{seconds:02d}s'.format(**d)
    elif minutes > 0:
        return '{sign}{minutes:02d}m:{seconds:02d}s'.format(**d)
    else:
        return '{sign}{seconds:02d}s'.format(**d)