code: public void addUniqueFields(FieldSet uniqueFields) {
  		if (this.uniqueFields == null) {
  			this.uniqueFields = new HashSet<FieldSet>();
  		}
  		this.uniqueFields.add(uniqueFields);
  	}
docs: Adds a combination of fields that are unique in these data properties.
  
  @param uniqueFields The fields that are unique in these data properties.