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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_in_reactor(url, callback, spider_cls=DefaultSpider, **kwargs):
 """Crawls given URL with given callback. Parameters url : str The URL to crawl. callback : callable Function to be used as callback for the request. spider_cls : scrapy.Spider (default: DefaultSpider) A spider class to be used in the crawler instance. kwargs : dict, optional Extra arguments to be passed to ``_run_spider_in_reactor``. Returns ------- crochet.EventualResult """

    spider_cls = override_start_requests(spider_cls, [url], callback)
    return _run_spider_in_reactor(spider_cls, **kwargs)