private static @Nullable @FileType String getFileTypefromExtension(String extension) {
    if (CONTENT_FILE_EXTENSION.equals(extension)) {
      return FileType.CONTENT;
    } else if (TEMP_FILE_EXTENSION.equals(extension)) {
      return FileType.TEMP;
    }
    return null;
  }
Categories for the different internal files a ShardedDiskStorage maintains. CONTENT: the file
that has the content TEMP: temporal files, used to write the content until they are switched to
CONTENT files
imagepipeline-base/src/main/java/com/facebook/cache/disk/DefaultDiskStorage.java