@Override
    public void putAll(Map<? extends K, ? extends V> m) {
        // will throw UnsupportedOperationException; delegate anyway for testability
        underlying().putAll(m);
    }
@param key the key
@param value the value
@return a wrapped hash-based persistent map that has a single mapping
@param <K> the key type
@param <V> the value type
server-common/src/main/java/org/apache/kafka/server/immutable/pcollections/PCollectionsImmutableMap.java