in src/geojson2h3.js [203:216]
function h3SetToMultiPolygonFeature(hexagons, properties = {}) {
const coordinates = hexagons.map(h3Index =>
// Wrap in an array for a single-loop polygon
[h3.h3ToGeoBoundary(h3Index, {geoJson: true})]
);
return {
type: FEATURE,
properties,
geometry: {
type: MULTI_POLYGON,
coordinates
}
};
}