/**
    Stack your data with `.stack()` from d3 - shape for stacked bar or area charts
    A wrapper around [d3-shape.stack](https://github.com/d3/d3-shape#stack)

    // Input data
    const data = [
    {month: '2015-01-01', apples: 320,  bananas: 480,  cherries: 640, dates: 400}
    {month: '2015-02-01', apples: 640,  bananas: 960,  cherries: 740, dates: 500},
    {month: '2015-03-01', apples: 1600, bananas: 1440, cherries: 920, dates: 600},
    {month: '2015-04-01', apples: 3840, bananas: 1920, cherries: 960, dates: 700},
  ];

    // Usage
    stack(data, ['apples', 'bananas', 'cherries', 'dates'])

    // Output data
    stackData equals an array of values. The `month` values you can't see because sneakily stashes them as a property on the array, accessible as `d.data`.
  [
        [ [   0, 320],  [   0,  640], [   0, 1600], [   0, 3840] ], // apples
        [ [ 320, 800],  [ 640, 1600], [1600, 3040], [3840, 5760] ], // bananas
        [ [ 800, 1440], [1600, 2340], [3040, 3960], [5760, 6720] ], // cherries
        [ [1440, 1840], [2340, 2840], [3960, 4560], [6720, 7420] ]  // dates
    ]

    @param {Array<any>} data The data to be stacked.
    @param {Array<string>|Function} keys The group names to stack, passed to `stack.keys()`.
    @param {Object} options Options object
    @param {string|number|Function} [options.value] An accessor function passed to `stack.value()`. If this is a string or number, it will be transformed into an accessor for that key.
    @param {Array<any>|Function} [options.order] The stack order passed to `stack.order()`.
    @param {Function} [options.offset] The offset function passed to `stack.offset()`.

    @returns {Array<any>} stackedData The transformed data
 */
export default function stack(data: Array<any>, keys: Array<string> | Function, { value, order, offset }?: {
    value?: string | number | Function | undefined;
    order?: Function | any[] | undefined;
    offset?: Function | undefined;
}): Array<any>;