def _process_spidermw_output(self, output, request, response, spider):
        """Process each Request/Item (given in the output parameter) returned
        from the given spider
        """
        if isinstance(output, Request):
            self.crawler.engine.crawl(request=output, spider=spider)
        elif isinstance(output, (BaseItem, dict)):
            self.slot.itemproc_size += 1
            dfd = self.itemproc.process_item(output, spider)
            dfd.addBoth(self._itemproc_finished, output, response, spider)
            return dfd
        elif output is None:
            pass
        else:
            typename = type(output).__name__
            logger.error('Spider must return Request, BaseItem, dict or None, '
                         'got %(typename)r in %(request)s',
                         {'request': request, 'typename': typename},
                         extra={'spider': spider})
Process each Request/Item (given in the output parameter) returned
        from the given spider
        
stackoverflow/venv/lib/python3.6/site-packages/scrapy/core/scraper.py