getEmptyState() {
        const pkIndex = {
            [this.arrName]: [],
            [this.mapName]: {},
        };
        const attrIndexes = Object.keys(this.fields)
            .filter((attr) => attr !== this.idAttribute)
            .filter((attr) => this.fields[attr].index)
            .reduce(
                (indexes, attr) => ({
                    ...indexes,
                    [attr]: {},
                }),
                {}
            );
        return {
            ...pkIndex,
            indexes: attrIndexes,
            meta: {},
        };
    }
Returns the default state for the data structure.
@return {Object} The default state for this {@link ORM} instance's data structure