public bool ReferencesAllFrames(string seriesInstanceUid, string sopInstanceUid)
 {
     if (_dictionary.ContainsKey(seriesInstanceUid))
     {
         ImageSopInstanceReferenceDictionary sopDictionary = _dictionary[seriesInstanceUid];
         if (sopDictionary == null || sopDictionary.ReferencesAllFrames(sopInstanceUid))
         {
             return(true);
         }
     }
     return(false);
 }