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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 config(_config=None, **kwargs):
 """ A decorator for setting the default kwargs of `BaseHandler.crawl`. Any self.crawl with this callback will use this config. """

    if _config is None:
        _config = {}
    _config.update(kwargs)

    def wrapper(func):
        func._config = _config
        return func
    return wrapper