@Override
    protected void transferValue(Pipe pipe, Input input, Output output, int number, boolean repeated)
            throws IOException
    {
        if (pipeSchema == null)
        {
            throw new RuntimeException("No pipe schema for value: " +
                    schema.typeClass().getName());
        }

        output.writeObject(number, pipe, pipeSchema, repeated);
    }
The pipe schema of the member (message).
protostuff-collectionschema/src/main/java/io/protostuff/MessageCollectionSchema.java