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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 seed(context, data):
 """Initialize a crawler with a set of seed URLs. The URLs are given as a list or single value to the ``urls`` parameter. If this is called as a second stage in a crawler, the URL will be formatted against the supplied ``data`` values, e.g.: https://crawl.site/entries/%(number)s.html """

    for key in ('url', 'urls'):
        for url in ensure_list(context.params.get(key)):
            url = url % data
            context.emit(data={'url': url})