类方法告诉我，我又使用了1个pos。争论比需要的，但我没有

我从代码中收到以下错误： TypeError: get_manifest() takes 0 positional arguments but 1 was given

我有一个class scan，并且get_manifest是一个函数scan：

import amfy
import requests
import json
from datetime import timedelta, datetime 
class Scan:
        def __init__(self, realm = 416, cluster = 9):

            self.events = list()
            self.url = "http://realm{}.c{}0.castle.rykaiju.com/api/locales/en/get_serialized_new".format(realm, cluster)


        def get_manifest():                 
            self.request = requests.get(self.url)

            if self.request.status_code == 200:
                self.manifest = self.request.json() if "json" in self.request.headers["content-type"] else amfy.loads(self.request.content)

            else:
                self.manifest = {"failed": req.reason}



        def get_time(day):

            self.today = datetime.now()

            self.plusdays = timedelta(days = day)

            self.new_date = sel.ftoday + self.plusdays

            self.year, self.month, self.day = self.new_date.year, self.new_date.month, self.new_date.day

            if len(str(self.day)) == 1:
                day = "0{}".format(self.day)

            if len(str(self.month)) == 1:
                month = "0{}".format(self.month)

            self.date = str(self.year) + str(self.month) + str(self.day)

            return self.date


        def search_events():

            for day in range(0, 11):
                date = self.get_time(day)

                for section in doaManifest:                
                    for key, value in doaManifest[section].items():                    
                        if date in key:
                            event_title = key 
                            try:
                                event_desc = value['text']
                            except KeyError:
                                event_desc = """" /!\ No Event Description /!\""""
                            my_dict = {'title' : event_title, 'contents' : event_desc}
                            self.events.append(my_dict)

然后，在另一个类中，即我的应用程序GUI（用tkinter编写），我有一个调用该类的按钮。该按钮的命令是这样的：

def scan(self):

    if self.scan['text'] == 'Scan':
        self.scan['text'] = 'Re-Scan'
        self.scanned = True

    self.scan = Scan()
    self.scan.get_manifest()
    self.scan.search_events()

我没有提出get_manifest任何论据，为什么它说我是？