code: protected void initModelFolder(Element root, CmsXmlContentDefinition contentDefinition) throws CmsXmlException {
  
          String master = root.attributeValue(APPINFO_ATTR_URI);
          if (master == null) {
              throw new CmsXmlException(
                  Messages.get().container(
                      Messages.ERR_XMLCONTENT_MISSING_MODELFOLDER_URI_2,
                      root.getName(),
                      contentDefinition.getSchemaLocation()));
          }
          m_modelFolder = master;
      }
docs: Initializes the folder containing the model file(s) for this content handler.<p>
  
  @param root the "modelfolder" element from the appinfo node of the XML content definition
  @param contentDefinition the content definition the model folder belongs to
  @throws CmsXmlException if something goes wrong