/** @return {@link #snapshotsByNames} as a {@link ReadOnlyList} */
 public ReadOnlyList<Snapshot> getSnapshotList() {
   return ReadOnlyList.Util.asReadOnlyList(snapshotsByNames);
 }
 /** @return {@link #snapshotsByNames} */
 ReadOnlyList<Snapshot> getSnapshotsByNames() {
   return ReadOnlyList.Util.asReadOnlyList(this.snapshotsByNames);
 }