public static String getTooltip(XmlElement element) {
   String notation = element.getNotation();
   String imageFilePath = getStructureImageFilePath(element);
   return getTooltip(notation, imageFilePath);
 }
 public static String getStructureImageFilePath(XmlElement element) {
   String fileName = element.getName();
   fileName = fileName + ".png";
   return NUCLEOTIDE_DIRECTORY + System.getProperty("file.separator") + fileName;
 }