docs: private String fetchRegionFromCache(String bucketName) {
          String bucketRegion = bucketRegionCache.get(bucketName);
          if (bucketRegion == null) {
              if (log.isDebugEnabled()) {
                  log.debug("Bucket region cache doesn't have an entry for " + bucketName
                          + ". Trying to get bucket region from Amazon S3.");
              }
  
              bucketRegion = getBucketRegionViaHeadRequest(bucketName);
  
              if (bucketRegion != null) {
                  bucketRegionCache.put(bucketName, bucketRegion);
              }
          }
          if (log.isDebugEnabled()) {
              log.debug("Region for " + bucketName + " is " + bucketRegion);
          }
          return bucketRegion;
      }