docs: static NavigableSet<ChannelSpec> asChannelSet(byte[] data)
              throws JSONException, IllegalArgumentException {
          ImmutableSortedSet.Builder<ChannelSpec> sbld = ImmutableSortedSet.naturalOrder();
          JSONArray ja = new JSONArray(new String(data, StandardCharsets.UTF_8));
          for (int i=0; i< ja.length(); ++i) {
              sbld.add(new ChannelSpec(ja.getString(i)));
          }
          return  sbld.build();
      }