private StoredValues singleValue(final int trimmedSize, final boolean trimTop) {
            final Iterable<StoredValues> values = getStoredValueIterable(trimmedSize, trimTop);
            final Iterator<StoredValues> iterator = values.iterator();
            if (iterator.hasNext()) {
                return iterator.next();
            }
            return null;
        }
Write data from the data store to an output removing them from the datastore as we go as they will be transferred
to another store.

@param output The output to write to.
stroom-query/stroom-query-common/src/main/java/stroom/query/common/v2/LmdbDataStore.java