docs: public Collection<JcrPropertyDefinition> getMandatoryPropertyDefinitions( Name primaryType,
                                                                                Set<Name> mixinTypes ) {
          if (mixinTypes.isEmpty()) {
              return mandatoryPropertiesNodeTypes.get(primaryType);
          }
          Set<JcrPropertyDefinition> defn = new HashSet<JcrPropertyDefinition>();
          defn.addAll(mandatoryPropertiesNodeTypes.get(primaryType));
          for (Name mixinType : mixinTypes) {
              defn.addAll(mandatoryPropertiesNodeTypes.get(mixinType));
          }
          return defn;
      }