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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 _check_rel(attrs, rel_whitelist, rel_blacklist):
 """ Check a link's relations against the whitelist or blacklist. First, this will reject based on blacklist. Next, if there is a whitelist, there must be at least one rel that matches. To explicitly allow links without a rel you can add None to the whitelist (e.g. ['in-reply-to',None]) """


        rels = attrs.get('rel', [None])

        if rel_blacklist:
            # Never return True for a link whose rel appears in the blacklist
            for rel in rels:
                if rel in rel_blacklist:
                    return False

        if rel_whitelist:
            # If there is a whitelist for rels, only return true for a rel that
            # appears in it
            for rel in rels:
                if rel in rel_whitelist:
                    return True
            # If there is a whitelist and we don't match, then reject
            return False

        return True