docs: public Properties setProperties(String pGroupKey, Properties pProperties) {
      XMLProperties old      = new XMLProperties();
      String        groupKey = pGroupKey;
  
      if (groupKey.charAt(groupKey.length()) != '.') {
        groupKey += ".";
      }
      Iterator iterator = pProperties.entrySet().iterator();
  
      while (iterator.hasNext()) {
        Map.Entry entry = (Map.Entry) iterator.next();
        String    key   = (String) entry.getKey();
        Object    obj   = setPropertyValue(groupKey + key, entry.getValue());
  
        // Return removed entries
        if (obj != null) {
          old.setPropertyValue(groupKey + key, entry.getValue());
        }
      }
      return ((old.size() > 0) ? old : null);
    }