code: function deleteKMS(region) {
    const regionKey = getRegionKey(region);
    if (regionKey) {
      kmsOptionsByRegionKey.delete(regionKey);
      return kmsByRegionKey.delete(regionKey);
    }
    return false;
  }
docs: Deletes the KMS instance cached for the given region (if any) and returns true if successfully deleted or false
  if it did not exist.
  @param {string} region - the AWS region to use as a key
  @returns {boolean} true if existed and deleted; false otherwise