Scrapy - CrawlSpiderで動的にURLを指定する

前提・実現したいこと

Scrapyでスクレイピングを行っています。
"県" "カテゴリ"を入れ替えながら、動的にURLを指定しようとした際に、エラーが起きてしまいました。

発生している問題・エラーメッセージ

Traceback (most recent call last):
  File "/home/ec2-user/venv/lib64/python3.7/site-packages/twisted/internet/defer.py", line 1418, in _inlineCallbacks
    result = g.send(result)
  File "/home/ec2-user/venv/lib64/python3.7/site-packages/scrapy/crawler.py", line 88, in crawl
    start_requests = iter(self.spider.start_requests())
TypeError: 'NoneType' object is not iterable

該当のソースコード

python
1class StorelistSpider(CrawlSpider):
2	name = "crawler"
3
4	# #パッチ間で永続的な状態を維持
5	# self.logger.info(self.state.get("state_key1"))
6	# self.state["state_key1"] = {"key":"value"}
7	# self.state["state_key2"] = 0
8
9	allowed_domains = ["example.com"]
10
11	def start_requests(self):
12		#Target Category
13		with open('CategoryList.txt') as f1:
14			for q1 in f1:
15				targetCategory = q1
16
17				#Target Prefecture
18				with open('prefectureList.txt') as f2:
19					for q2 in f2:
20						prefectureName = q2
21
22
23						start_urls=("https://example.com/" + q2 + "/")
24
25						#rules to follow links:
26						rules = (
27							#follow area link first, then category link next, check list pages and go to the details
28							Rule(LinkExtractor(
29								allow=r"/\w+/A\d{4}/$",
30								restrict_xpaths = "//*[@id='js-leftnavi-area-scroll']",
31								unique = True,)),
32							Rule(LinkExtractor(
33								allow=r"/\w+/A\d{4}/rstLst/" + "{}".format(targetCategory) + r"/$",
34								restrict_xpaths = "//*[@id='js-leftnavi-genre-balloon']",
35								unique = True,)),
36							Rule(LinkExtractor(
37								allow=r"/\w+/A\d{4}/rstLst/" + "{}".format(targetCategory) + r"/\d*/$",
38								restrict_xpaths = "//*[@id='container']/div[15]/div[4]/div/div[7]/div/ul",
39								unique = True,)),
40							Rule(LinkExtractor(
41								allow=r"/\w+/A\d{4}/A\d{6}/\d+/$",
42								restrict_xpaths = "//*[@id='container']/div[15]/div[4]/div/div[6]",
43								unique = True,
44							), callback="page_parse"),
45						)
46
47	def page_parse(self, response):
48		yield Page.from_response(response)
49
50