@NotNull
  private ConcurrentMap<VirtualFile, FileViewProvider> getVFileToViewProviderMap() {
    ConcurrentMap<VirtualFile, FileViewProvider> map = myVFileToViewProviderMap.get();
    if (map == null) {
      map = ConcurrencyUtil.cacheOrGet(myVFileToViewProviderMap, CollectionFactory.createConcurrentWeakValueMap());
    }
    return map;
  }
@NotNull
  private ConcurrentMap<VirtualFile, FileViewProvider> getVFileToViewProviderMap()