import type { ChartExcelExtractor } from "./types.js";
/**
 * Heatmap data is sparse `[xIndex, yIndex, value]` tuples against two axes. The export
 * stays sparse: one row per entry the user supplied, so a cell with no data has no row
 * rather than a `null` one. Its `valueFormatter` is the only one keyed by axis indices
 * instead of a data index, and the only one that is optional after defaultizing.
 */
export declare const heatmapExtractor: ChartExcelExtractor<'heatmap'>;