public void maybeAddAll(List<?> candidateList) {
        for (Object candidate : candidateList) {
            this.maybeAdd(candidate);
        }
    }
Add all items who implement {@link ClusterResourceListener} from the list.
@param candidateList List of objects which might implement {@link ClusterResourceListener}
clients/src/main/java/org/apache/kafka/common/internals/ClusterResourceListeners.java