code: public static <K> void updateWeights(double l2, double learningRate, Map<K, Double> weights, Map<K, Double> newWeights) {
          if(l2 > 0.0) {
              for(Map.Entry<K, Double> e : weights.entrySet()) {
                  K column = e.getKey();
                  newWeights.put(column, newWeights.get(column) + l2*e.getValue()*(-learningRate));
              }
          }
      }
docs: Updates the weights by applying the L2 regularization.
  
  @param l2
  @param learningRate
  @param weights
  @param newWeights
  @param <K>