@Override
            protected void addValueFrom(Input input,
                    Collection<Object> collection) throws IOException
            {
                final Object value = input.mergeObject(collection,
                        strategy.POLYMORPHIC_POJO_ELEMENT_SCHEMA);

                if (input instanceof GraphInput
                        && ((GraphInput) input).isCurrentMessageReference())
                {
                    collection.add(value);
                }
            }
For lazy initialization called by {@link RuntimeFieldFactory}.
protostuff-runtime/src/main/java/io/protostuff/runtime/RuntimeCollectionFieldFactory.java