public void addCustomRollUpMask(final CustomRollUpMask customRollUpMask) {
        if (customRollUpMasks == null) {
            customRollUpMasks = new HashSet<>();
        }

        customRollUpMasks.add(customRollUpMask);
    }
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/StroomStatsStoreEntityData.java