Method map

src/data/DataStore.ts:797–802

* Data mapping to a new List with given dimensions

(dims: DimensionIndex[], cb: MapCb)

     * Data mapping to a new List with given dimensions
     */
    map(dims: DimensionIndex[], cb: MapCb): DataStore {
        // TODO only clone picked chunks.
        const target = this.clone(dims);
        this._updateDims(target, dims, cb);
        return target;
    }

    /**
     * @caution Danger!! Only used in dataStack.