docs: public void rnnClearPreviousState() {
          if (layers == null)
              return;
          for (Layer layer : layers) {
              if (layer instanceof RecurrentLayer)
                  ((RecurrentLayer) layer).rnnClearPreviousState();
              else if (layer instanceof MultiLayerNetwork) {
                  ((MultiLayerNetwork) layer).rnnClearPreviousState();
              }
          }
      }