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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 timestamp(stamp, tolerance=150):
 """Validate timestamp specified by request. See `validate.request` for additional info. Args: stamp: str. Time request was made as ISO 8601 timestamp. tolerance: int. Number of seconds request remains valid from timestamp. Returns bool: True if valid, False otherwise. """

    try:
        tolerance = datetime.timedelta(0, tolerance)
        timestamp_low = dateutil.parser.parse(stamp)
        timestamp_high = timestamp_low + tolerance
        now = datetime.datetime.now(timestamp_low.tzinfo)
    except ValueError:
        return False

    return now >= timestamp_low and now <= timestamp_high