@JsonPropertyDescription(DESCRIPTION_PREFIX + "the total size in bytes of the off heap reference data store.")
    @JsonProperty("refDataStoreSize")
    public List<DocRef> getRefDataStoreSize() {
        return refDataStoreSize;
    }
Create a list of {@link DocRef} objects that are associated with a single {@link InternalStatisticKey}
stroom-statistics/stroom-statistics-impl/src/main/java/stroom/statistics/impl/InternalStatisticsConfig.java