code: public Optional<DataDirEntry> maybeGetDataDirEntry(DataDirectoryKey key) {
  		return Optional.fromNullable(dataDirectory.get(key));
  	}
docs: Returns the optional data directory entry for the given key or absent if
  entry doesn't exist.
  
  @param key
  @return the data directory entry for the given key or absent if entry
  doesn't exist.