/**
    Calculate the extents of desired fields, skipping `false`, `undefined`, `null` and `NaN` values
    For example, data like this:
    [{ x: 0, y: -10 }, { x: 10, y: 0 }, { x: 5, y: 10 }]
    and a fields object like this:
    `{'x': d => d.x, 'y': d => d.y}`
    returns an object like this:
    `{ x: [0, 10], y: [-10, 10] }`
    @param {Array<object>} data A flat array of objects.
    @param {Record<string, Function>} fields An object containing field names as keys and accessor functions as values. If an accessor function returns an array of values, each value will also be evaluated.
    @returns {Record<string, [any, any]>} An object with the same structure as `fields` but instead of an accessor, each key contains an array of a min and a max.
*/
export default function calcExtents(data: Array<object>, fields: Record<string, Function>): Record<string, [any, any]>;