code: function getKMSOptionsUsed(region) {
    const regionKey = getRegionKey(region);
    return regionKey ? kmsOptionsByRegionKey.get(regionKey) : undefined;
  }
docs: Gets the kms options used to construct the KMS instance cached for the given region (if specified and if
  previously cached); otherwise for the current region (if previously cached); otherwise returns undefined.
  @param {string} [region] - the optional AWS region to use - defaults to current AWS region if not specified
  @returns {AWS.KMS|undefined} the kms options used to construct the KMS instance cached for the given or
  current region (if any); otherwise returns undefined