public HashSet<string> FindObsoleteVersions() {
HashSet<string> obsoleteFiles = new HashSet<string>();
int versionIndex = 0;
int numberOfVersions = Values.Count;
foreach (var metadata in Values) {
versionIndex++;
if (versionIndex < numberOfVersions) {
obsoleteFiles.Add(metadata.filename);
}
}
return obsoleteFiles;
}
}