code: private static void appendListProperty(List<Object> dest, Configuration config,
              String key)
      {
          Object value = config.getProperty(key);
          if (value != null)
          {
              if (value instanceof Collection)
              {
                  Collection<?> col = (Collection<?>) value;
                  dest.addAll(col);
              }
              else
              {
                  dest.add(value);
              }
          }
      }
docs: Adds the value of a property to the given list. This method is used by
  {@code getList()} for gathering property values from the child
  configurations.
  
  @param dest the list for collecting the data
  @param config the configuration to query
  @param key the key of the property