code: public boolean isETag( Name primaryType,
                             Set<Name> mixinTypes ) {
          if (etagNodeTypeNames.contains(primaryType)) return true;
          if (mixinTypes != null) {
              for (Name mixinType : mixinTypes) {
                  if (etagNodeTypeNames.contains(mixinType)) return true;
              }
          }
          return false;
      }
docs: Determine if at least one of the named primary node type or mixin types is or subtypes the 'mix:etag' mixin type.
  
  @param primaryType the primary type name; may not be null
  @param mixinTypes the mixin type names; may be null or empty
  @return true if any of the named node types has an ETag, or false if there are none