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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 timeuntil(d, now=None):
 """ Like timesince, but returns a string measuring the time until the given time. """

    if not now:
        if getattr(d, 'tzinfo', None):
            now = datetime.datetime.now(LocalTimezone(d))
        else:
            now = datetime.datetime.now()
    return timesince(now, d)