code: public static String link(Key k, String content, Key cp, String response, Key val) {
      DeepLearning req = new DeepLearning();
      RString rs = new RString("<a href='" + req.href() + ".query?source=%$key" +
              (cp == null ? "" : "&checkpoint=%$cp") +
              (response == null ? "" : "&response=%$resp") +
              (val == null ? "" : "&validation=%$valkey") +
              "'>%content</a>");
      rs.replace("key", k.toString());
      rs.replace("content", content);
      if (cp != null) rs.replace("cp", cp.toString());
      if (response != null) rs.replace("resp", response);
      if (val != null) rs.replace("valkey", val);
      return rs.toString();
    }
docs: Return a query link to this page
  @param k Model Key
  @param content Link text
  @param cp Key to checkpoint to continue training with (optional)
  @param response Response
  @param val Validation data set key
  @return HTML Link