code: private void addPropertyCounters(UsageStatistics usageStatistics,
  			PropertyIdValue property) {
  		if (!usageStatistics.propertyCountsMain.containsKey(property)) {
  			usageStatistics.propertyCountsMain.put(property, 0);
  			usageStatistics.propertyCountsQualifier.put(property, 0);
  			usageStatistics.propertyCountsReferences.put(property, 0);
  		}
  	}
docs: Initializes the counters for a property to zero if not done yet.
  
  @param usageStatistics
  statistics object to initialize
  @param property
  the property to count