code: @VisibleForTesting
  	static String constructCounterShardIdentifier(final String counterName, final int shardNumber)
  	{
  		Preconditions.checkNotNull(counterName);
  		Preconditions.checkArgument(!StringUtils.isBlank(counterName),
  			"CounterData Names may not be null, blank, or empty!");
  		Preconditions.checkArgument(shardNumber >= 0, "shardNumber must be greater than or equal to 0!");
  
  		return counterName + COUNTER_SHARD_KEY_SEPARATOR + shardNumber;
  	}
docs: Helper method to set the internal identifier for this entity.
  
  @param counterName
  @param shardNumber A unique identifier to distinguish shards for the same {@code counterName} from each other.