docs: private Optional<? extends SoyMsgBundle> mergeMsgBundles(final Locale locale, final List<SoyMsgBundle> soyMsgBundles) {
          if (soyMsgBundles.isEmpty()) {
              return Optional.absent();
          }
  
          final List<SoyMsg> msgs = Lists.newArrayList();
          for (final SoyMsgBundle smb : soyMsgBundles) {
              for (final Iterator<SoyMsg> it = smb.iterator(); it.hasNext();) {
                  msgs.add(it.next());
              }
          }
  
          return Optional.of(new SoyMsgBundleImpl(locale.toString(), msgs));
      }