code: public long numParams() {
          int ret = 0;
          for (Map.Entry<String, INDArray> entry : params.entrySet()) {
              ret += entry.getValue().length();
          }
          return ret;
      }
docs: The number of parameters for the model, for backprop (i.e., excluding visible bias)
  @return the number of parameters for the model (ex. visible bias)