有没有办法等待循环完成所有的scrapy.request，然后再做些什么呢？在这个例子中，我希望在for循环之后产生负载，因为我不想在每个分页（parse_stores）中产生负载，我只想在for之后的parse函数中产生负载。

import scrapy
import json
import math

class UnitsSpider(scrapy.Spider):
    """ docstrings """
    name = 'units'

    def start_requests(self):

        urls = [{
            "url":
            "https://url.com/"
        }, {
            "url":
            "https://url2.com"
        }]

        for url in urls:
            yield scrapy.Request(
                url['url'],
                meta={
                    'playwright': True,
                }
            )

    def parse(self, response):

        url = response.url

        data = response.css('script#__NEXT_DATA__::text').get()
        json_data = json.loads(data)

        total_pages = math.ceil(
            json_data['props']['pageProps']['totalStores'] / 50)

        payload = {
            'base_url': url,
            'stores': 0,
            'stores_data': []
        }

        for page in range(0, total_pages):
            next_page = f'{url}{page + 1}'

            req = response.follow(url=next_page)

            yield scrapy.Request(url=req.url, callback=self.parse_stores, meta={
                'playwright': True}, cb_kwargs={'payload': payload})

        # here after all the requests are done i'd like to do something    

    def parse_stores(self, response, payload):
        data = response.css('script#__NEXT_DATA__::text').get()
        json_data = json.loads(data)

        stores = json_data['props']['pageProps']['cityData']['stores']

        payload['stores'] += len(stores)
        # append stores to stores_data
        payload['url'] = response.url
        yield payload