public bool AcquireNextUnindexedZip(out string zip)
 {
     lock (_lock)
     {
         zip = _unindexedZips.FirstOrDefault();
         if (zip != null)
         {
             _unindexedZips.Remove(zip);
             return(true);
         }
         return(false);
     }
 }
 public bool AcquireNextUnmergedZipGroup(out IKaVESet <string> zips)
 {
     lock (_lock)
     {
         zips = _zipGroups.FirstOrDefault();
         if (zips != null)
         {
             _zipGroups.Remove(zips);
             return(true);
         }
         return(false);
     }
 }