code: private static List<Subchannel> filterNonFailingSubchannels(
        Collection<Subchannel> subchannels) {
      List<Subchannel> readySubchannels = new ArrayList<>(subchannels.size());
      for (Subchannel subchannel : subchannels) {
        if (isReady(subchannel)) {
          readySubchannels.add(subchannel);
        }
      }
      return readySubchannels;
    }
docs: Filters out non-ready subchannels.