Method getShallow

src/model/Model.ts:120–134

(
        key: R, ignoreParent?: boolean
    )

    }

    getShallow<R extends keyof Opt>(
        key: R, ignoreParent?: boolean
    ): Opt[R] {
        const option = this.option;

        let val = option == null ? option : option[key];
        if (val == null && !ignoreParent) {
            const parentModel = this.parentModel;
            if (parentModel) {
                // FIXME:TS do not know how to make it works
                val = parentModel.getShallow(key);
            }
        }
        return val as Opt[R];
    }

    // TODO At most 3 depth?
    getModel<R extends keyof Opt>(