code: private Map<UUID, Long> getExtendedAttributes(AttributeUpdaterOperation operation) {
          Collection<AttributeUpdate> updates = operation.getAttributeUpdates();
          if (updates == null) {
              return Collections.emptyMap();
          }
  
          return updates.stream()
                  .filter(au -> !Attributes.isCoreAttribute(au.getAttributeId()))
                  .collect(Collectors.toMap(AttributeUpdate::getAttributeId, AttributeUpdate::getValue));
      }
docs: Collects the extended Attributes from the AttributeUpdates of the given operation.