code: @VisibleForTesting
  	protected void assertCounterDetailsMutatable(final String counterName, final CounterStatus counterStatus)
  	{
  		Preconditions.checkNotNull(counterName);
  		Preconditions.checkNotNull(counterStatus);
  
  		if (counterStatus != CounterStatus.AVAILABLE && counterStatus != CounterStatus.READ_ONLY_COUNT)
  		{
  			final String msg = String.format("Can't mutate with status %s.  Counter must be in in the %s or %s state!",
  				counterStatus, CounterStatus.AVAILABLE, CounterStatus.READ_ONLY_COUNT);
  			throw new CounterNotMutableException(counterName, msg);
  		}
  	}
docs: Helper method to determine if a counter's incrementAmount can be mutated (incremented or decremented). In order
  for that to happen, the counter's status must be {@link CounterStatus#AVAILABLE}.
  
  @param counterName The name of the counter.
  @param counterStatus The {@link CounterStatus} of a counter that is currently stored in the Datastore.
  @return