code: @Override
  	public List<String> getHeadLines(final String type) {
  		ArrayList<String> lines = headers.get(type);
  		return lines == null ? null : Collections.unmodifiableList(lines);
  	}
docs: Gets the head lines, of a specified type.
  
  @param type the type of lines to retrieve.
  @return a list of headlines, or null if there are no headlines of the given type.