@Override
    public void writeTo(Output output, Collection<V> message) throws IOException
    {
        if (preserveNull)
            writeWithNullTo(output, message);
        else
            writeWithoutNullTo(output, message);
    }
Transfers the value from the input to the output.
protostuff-collectionschema/src/main/java/io/protostuff/CollectionSchema.java