internal static IEnumerable <string> Get(string key)
 {
     if (!_cache.IsActual)
     {
         lock (_sync)
         {
             if (!_cache.IsActual)
             {
                 _cache = new FileCache();
             }
         }
     }
     if (!_cache.Files.ContainsKey(key))
     {
         throw new ApplicationException($"An object with key {key} does not exists");
     }
     return(_cache.Files[key]);
 }
 static FileCacheStore()
 {
     _cache = new FileCache();
     _sync  = new object();
 }