@Override
    public long expireAfterUpdate(
        DimensionCacheKey key, DimensionData value, long currentTime, long currentDuration) {
      return currentDuration;
    }
Create a new DimensionSource that will cache the results from another {@link DimensionSource}

@param source
@param config - config used to configure the expiry (ttl) for entries in the cache
@return a new CachingDimensionSource
src/main/java/io/prometheus/cloudwatch/CachingDimensionSource.java