code: @Override
  	public void addUniqueHeadLine(final String type, final String aLine) {
  		ArrayList<String> lines = headers.get(type);
  
  		if (lines == null) {
  			lines = new ArrayList<>();
  			lines.add(aLine);
  			headers.put(type, lines);
  		} else if (!lines.contains(aLine)) {
  			lines.add(aLine);
  		}
  	}
docs: Records a line for inclusion in the html/head, if it has not already been included.
  
  @param type the type of line.
  @param aLine the line to include.