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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 _normalize_interval(start, end, value):
 """Normalize datetime intervals. Given a pair of datetime.date or datetime.datetime objects, returns a 2-tuple of tz-aware UTC datetimes spanning the same interval. For datetime.date objects, the returned interval starts at 00:00:00.0 on the first date and ends at 00:00:00.0 on the second. Naive datetimes are upgraded to UTC. Timezone-aware datetimes are normalized to the UTC tzdata. Params: - start: A date or datetime - end: A date or datetime """

    if not isinstance(start, datetime):
        start = datetime.combine(start, START_OF_DAY)
        end = datetime.combine(end, START_OF_DAY)

    if start.tzinfo is None:
        start = pytz.UTC.localize(start)
        end = pytz.UTC.localize(end)
    else:
        start = start.astimezone(pytz.UTC)
        end = end.astimezone(pytz.UTC)

    return start, end