code: public ConfigBase fromXml(final InputStream is,
                              final Class cl) throws ConfigException {
      try {
        return fromXml(parseXml(is), cl);
      } catch (final ConfigException ce) {
        throw ce;
      } catch (final Throwable t) {
        throw new ConfigException(t);
      }
    }
docs: XML root element must have type attribute if cl is null
  
  @param is an input stream
  @param cl class of object or null
  @return parsed notification or null
  @throws ConfigException on error