how to make Mutation by graphene-django when there are no input, output?

Question

when user click button, I want to update A(Stock) DB by using data from B(Account) DB.

when user click button, django get data(company_id and company_secret) From Account DB. and then web scraping with data. it makes new data. i want to just save new data to Stock DB. I don't want to give data to web.

below code show error "GetStockMutation fields must be a mapping (dict / OrderedDict) with field names as keys or a function which returns such a mapping."

import graphene
from .types import AccountType, StockType
from .models import *
from .crypt import AESCipher
from graphql_jwt.decorators import login_required
from .views import getStockNamu

class GetStockMutation(graphene.Mutation):

    @login_required
    def mutate(self, info, **kwargs):
        if info.context.user.is_authenticated:
            user_id = info.context.user.id
            
            #data from Account DB
            account = Account.objects.get(user_id=user_id, company=1)
            
            #decrypt
            company_id = AESCipher().decrypt_str(account.company_id)
            company_secret = AESCipher().decrypt_str(account.company_secret)

            # web scraping
            code, amount = getStockNamu(company_id, company_secret)
           
            #save it to Stock DB
            stock = Stock.objects.create(user_id=user_id, code=code, amount=amount, company=1)
            stock.save()
            print(stock)
        else:
            raise PermissionError("로그인이 필요합니다.")



class Query(object):
    pass

        
class Mutation(graphene.ObjectType):
    get_account = GetaccountMutation.Field()
    get_stock = GetStockMutation.Field()