schema.py

from ariadne import gql 

type_defs = gql("""
    scalar Datetime

    type User {
        id: Int!
        name: String!
        email: String!
        password: String!
        created_at: Datetime!
        todos: [Todo]
    }

    type Todo {
        id: Int!
        text: String!
        is_done: Boolean!
        created_at: Datetime!
        created_by: User!
        owner: User!
    }

    input AddUserInput {
        name: String!
        email: String!
        password: String!
    }
    input AddTodoInput {
        text: String!
        created_by: Int!
        is_done: Boolean!
    }

    input UpdateUserInput {
        id: Int!
        name: String
        email: String
        password: String
    }

    input UpdateTodoInput {
        id: Int!
        text: String
        is_done: Boolean
    }
    
    type Mutation {
        addUser(user: AddUserInput!): User!
        deleteUser(userId: Int!): Boolean
        updateUser(user: UpdateUserInput!): User!
        addTodo(todo: AddTodoInput!): Todo!
        deleteTodo(todoId: Int!): Boolean
        updateTodo(todo: UpdateTodoInput!): Todo!
    }

    type Query {
        todos: [Todo!]
        users: [User!]
        todo(todoId: Int!): Todo
        getTodosByUser(userId: Int!): [Todo!]
        user(userId: Int!): User
    }
""")