用石墨烯组织GraphQL突变

Question

我正在尝试组织我的突变，以使它们不全都位于顶层。这是我要放在“会话”部分下的一系列突变：

import graphene
from django.contrib.auth import authenticate
from rest_framework.authtoken.models import Token


class Login(graphene.Mutation):
    token = graphene.String()
    username = graphene.String()
    user_id = graphene.Int()

    class Arguments:
        username = graphene.String(required=True)
        password = graphene.String(required=True)

    def mutate(self, info, **kwargs):
        username = kwargs.get('username', '').strip()
        password = kwargs.get('password', '').strip()
        if username and password:
            # Test username/password combination
            user = authenticate(username=username, password=password)
            # Found a match
            if user is not None and user.is_active:
                token = Token.objects.get_or_create(user=user)[0]
                # return HttpResponse(token.key, content_type='text/plain')
                return Login(token=token.key, username=user.username, user_id=user.id)
        # credential check failed
        return Login()


class Logout(graphene.Mutation):
    success = graphene.Boolean()

    def mutate(self, info):
        if info.context.user is not None:
            info.context.user.token.delete()
        return Logout(success=True)


class SessionsMutations(graphene.ObjectType):
    login = Login.Field()
    logout = Logout.Field()

当我直接混入SessionsMutations对象时，这些突变会出现在顶层并且可以正常工作。

class Query():
    pass

class Mutation(SessionsMutations):
    pass

schema = graphene.Schema(query=Query, mutation=Mutation)

当我尝试将SessionsMutations定义为字段时，我可以成功向login提交查询，但是会话始终返回null，并且永远不会运行变异代码。

class Query():
    pass

class Mutation():
    session = graphene.Field(SessionsMutations)

schema = graphene.Schema(query=Query, mutation=Mutation)

我需要设置什么以便可以接受有组织的突变？