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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 crawl(url, callback, **kwargs):
 """Crawls an URL with given callback. Parameters url : str An URL to crawl. callback : callable A function to be used as spider callback for the given URL. spider_cls : scrapy.Spider (default: DefaultSpider) A spider class to be used in the crawler instance. capture_items : bool (default: True) If enabled, the scraped items are captured and returned. return_crawler : bool (default: False) If enabled, the crawler instance is returned. If ``capture_items`` is enabled, the scraped items is collected in ``crawler.items``. settings : dict, optional Custom crawler settings. timeout : int, (default: DEFAULT_TIMEOUT) Result wait timeout. Returns ------- out By default, the scraped items. If ``return_crawler`` is ``True``, returns the crawler instance. Raises ------ crochet.TimeoutError """

    timeout = kwargs.pop('timeout', DEFAULT_TIMEOUT)
    return wait_for(timeout, _crawl_in_reactor, url, callback, **kwargs)