void (K key, @NotNull Iterable<? extends V> values) { try { myMap.appendData(key, new AppendablePersistentMap.ValueDataAppender() { @Override public void append(@NotNull DataOutput out) throws IOException { for (V v : values) { myValuesExternalizer.save(out, v); } } }); } catch (IOException e) { throw new BuildDataCorruptedException(e); } }