code: protected void addConfiguration(
          CmsXmlContentDefinition contentDefinition,
          String elementName,
          String configurationValue)
      throws CmsXmlException {
  
          if (!elementName.contains("/") && (contentDefinition.getSchemaType(elementName) == null)) {
              throw new CmsXmlException(
                  Messages.get().container(Messages.ERR_XMLCONTENT_CONFIG_ELEM_UNKNOWN_1, elementName));
          }
  
          m_configurationValues.put(elementName, configurationValue);
      }
docs: Adds a configuration value for an element widget.<p>
  
  @param contentDefinition the XML content definition this XML content handler belongs to
  @param elementName the element name
  @param configurationValue the configuration value to use
  
  @throws CmsXmlException in case an unknown element name is used