handle multiple type and check if there is key inside that object in typescript

export interface UserDocument {
    _id: Types.ObjectId;
    phoneNumber: string;
    username: string;
    password: string;
    family: string;
    name: string;
    gender: GenderEnum;
    createdAt?: Date | any;
    updatedAt?: Date | any;
}
export interface CommentDocument {
    _id?: string;
    owner?: string | ObjectId | User;
    title?: string;
    text: string;
    isVerified?: boolean;
    createdAt?: Date;
    updatedAt?: Date;
}

function isUser(user: any): user is User {
    return 'phoneNumber' in user;
}

export class CommentOutputDto {
    constructor(data: CommentDocument) {
        this._id = data._id?.toString();
        if (isUser(data.owner)) {
            this.owner = {
                _id: data.owner._id.toString(),
                name: data.owner.name,
                lastname: data.owner.lastname,
            };
        }
        /* ... */
    }
    _id: string;

    owner?: Partial<User>;
}