code: public String forCaseInstance(String alias, String caseId) {
          return registry.getContainerId(alias, new ByCaseIdContainerLocator(caseId));
      }
docs: Looks up container id for given alias that is associated with case instance
  @param alias container alias
  @param caseId unique case instance id
  @return
  @throws IllegalArgumentException in case there are no containers for given alias