function cellToChildrenSize(h3Index, res) {
    if (!isValidCell(h3Index)) {
        throw H3LibraryError(E_CELL_INVALID);
    }
    const [lower, upper] = h3IndexToSplitLong(h3Index);
    const countPtr = C._malloc(SZ_INT64);
    try {
        throwIfError(H3.cellToChildrenSize(lower, upper, res, countPtr));
        return readInt64AsDoubleFromPointer(countPtr);
    } finally {
        C._free(countPtr);
    }
}
Get the number of children for a cell at a given resolution
@static
@param  {H3IndexInput} h3Index  H3 index to get child count for
@param  {number} res            Child resolution
@return {number}                Number of children at res for the given cell
@throws {H3Error}               If cell or parentRes are invalid