code: public static Map<String, String> mergeDefaults(
          CmsObject cms,
          Map<String, CmsXmlContentProperty> propertyConfig,
          Map<String, String> properties) {
  
          Map<String, String> result = new HashMap<String, String>();
          if (propertyConfig != null) {
              for (Map.Entry<String, CmsXmlContentProperty> entry : propertyConfig.entrySet()) {
                  CmsXmlContentProperty prop = entry.getValue();
                  String value = getPropValueIds(cms, prop.getType(), prop.getDefault());
                  if (value != null) {
                      result.put(entry.getKey(), value);
                  }
              }
          }
          result.putAll(properties);
          return result;
      }
docs: Extends the given properties with the default values
  from property configuration.<p>
  
  @param cms the current CMS context
  @param propertyConfig the property configuration
  @param properties the properties to extend
  
  @return a merged map of properties