public void clearCustomRollUpMask() {
        if (customRollUpMasks != null) {
            customRollUpMasks.clear();
        }
    }
Held in a set to prevent duplicates.
<p>
XMLTransient to force JAXB to use the setter
stroom-legacy/stroom-legacy-model_6_1/src/main/java/stroom/legacy/model_6_1/StatisticsDataSourceData.java