CreateUser class with graphene

main.py

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

    ok = graphene.Boolean()
    user = graphene.Field(lambda: UserInfoSchema)

    @staticmethod
    def mutate(root, info, username, password, fullname, ):
        hashed_password = bcrypt.hashpw(password.encode('utf-8'), bcrypt.gensalt())
        user = UserInfoSchema(username=username, password=hashed_password, fullname=fullname)
        ok = True
        db_user = crud.get_user_by_username(db, username=username)
        if db_user:
            raise GraphQLError("Username already registered")
        user_info = UserCreate(username=username, password=password, fullname=fullname)
        crud.create_user(db, user_info)
        return CreateUser(user=user, ok=ok)