code: protected UUID getBackpointerAttributeKey(long offset) {
          Preconditions.checkArgument(offset >= 0, "offset must be a non-negative number.");
          return new UUID(TableBucket.BACKPOINTER_PREFIX, offset);
      }
docs: Generates a 16-byte UUID that encodes the given Offset as a Backpointer (to some other offset).
  Format {0(64)}{Offset}
  - MSB is 0
  - LSB is Offset.
  
  @param offset The offset to generate a backpointer from.
  @return A UUID representing the Attribute Key.