private <T> T onMap(Function<RMapCache<String, String>, T> func) {
        final RMapCache<String, String> map = client.getMapCache(prefix);
        return func.apply(map);
    }
Pass an {@link RMap} to the function and return its result.

@param func the function to apply using the {@link RMap}
@return the result
gateway/engine/redis/src/main/java/io/apiman/gateway/engine/redis/common/RedisBackingStore.java