code: public static boolean isInlineChecksumBlockFilename(String fileName) {
      if (!isBlockFileName(fileName)) {
        return false;
      }
      int index_sep = fileName.indexOf('_', Block.BLOCK_FILE_PREFIX.length());
      return index_sep > 0 && fileName.indexOf('.', index_sep) < 0;
    }
docs: Determine whether the file name is for a inline checksum block.
  Inline checksum blocks are of this format:
  blk_(blockId)_(generation_id)_(version)_(checksum_type)_(bytes_per_checksum)
  @param fileName
  @return