code: public static Key<CounterShardData> key(final Key<CounterData> counterDataKey, final int shardNumber)
  	{
  		// Preconditions checked by #constructCounterShardIdentifier
  		return Key.create(CounterShardData.class,
  			constructCounterShardIdentifier(counterDataKey.getName(), shardNumber));
  	}
docs: Create a {@link Key Key<CounterShardData>}. Keys for this entity are not "parented" so that they can be added
  under high volume load in a given application. Note that CounterData will be in a namespace specific.
  
  @param counterDataKey
  @param shardNumber
  @return