@PipelineProperty(description = "Choose how frequently streams are rolled.",
            defaultValue = "1h",
            displayPriority = 4)
    public void setFrequency(final String frequency) {
        super.setFrequency(frequency);
    }
Joins text instances into a single text instance.
stroom-pipeline/src/main/java/stroom/pipeline/writer/RollingStreamAppender.java