public static short[] accountContainerIdFromPartitionClassStatsKey(String accountContainerKey) {
    String[] parts = accountContainerKey.split(Utils.ACCOUNT_CONTAINER_SEPARATOR);
    short accountId = Short.valueOf(parts[0].substring(2, parts[0].length() - 1));
    short containerId = Short.valueOf(parts[1].substring(2, parts[1].length() - 1));
    return new short[]{accountId, containerId};
  }
Return account id and container id from PartitionClassReport stats account container entry key. It's the opposite
of {@link #partitionClassStatsAccountContainerKey}. It returns an array of short with exactly two elements. The first
is the account id and the second is the container id.
@param accountContainerKey The account container entry key in PartitionClassReport stats.
@return An array of shorts with account id being the first element and container id being the second element.
ambry-utils/src/main/java/com/github/ambry/utils/Utils.java