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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 tag(*tags):
    '''
    Constructs a decorator that tags a function with specified
    strings (@tags). The tags on the decorated function are
    available via fn.tags
    '''
    def dfn(fn):
        _tags = getattr(fn, 'tags', set())
        _tags.update(tags)
        fn.tags = _tags
        return fn
    return dfn