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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 parse_date(s):
 """ Parse a date using dateutil.parser.parse if available, falling back to datetime.datetime.strptime if not """

    if isinstance(s, (datetime.datetime, datetime.date)):
        return s
    try:
        from dateutil.parser import parse
    except ImportError:
        parse = lambda d: datetime.datetime.strptime(d, "%Y-%m-%d")
    return parse(s)