@PipelineProperty(
            description = "The stream type that the output stream should be written as. This must be specified.",
            displayPriority = 1)
    public void setStreamType(final String streamType) {
        this.streamType = streamType;
    }
Joins text instances into a single text instance.
stroom-pipeline/src/main/java/stroom/pipeline/writer/RollingStreamAppender.java