function childPosToCell(childPos, h3Index, childRes) {
    const [cpLower, cpUpper] = numberToSplitLong(childPos);
    const [lower, upper] = h3IndexToSplitLong(h3Index);
    const child = C._malloc(SZ_H3INDEX);
    try {
        throwIfError(H3.childPosToCell(cpLower, cpUpper, lower, upper, childRes, child));
        return validateH3Index(readH3IndexFromPointer(child));
    } finally {
        C._free(child);
    }
}
Get the child cell at a given position within an ordered list of all children
at the specified resolution
@static
@param  {number} childPos       Position of the child cell to get
@param  {H3IndexInput} h3Index  H3 index of the parent cell
@param  {number} childRes       Resolution of child cell to return
@return {H3Index}          H3 index of child
@throws {H3Error}          If input is invalid