text: 
  np.random.seed(2020)  # set random seed
  X_noisy = add_noise(X, .2)
  score_noisy, evectors_noisy, evals_noisy = pca(X_noisy)
  variance_explained_noisy = get_variance_explained(evals_noisy)
  
  with plt.xkcd():
    plot_MNIST_sample(X_noisy)
    plot_variance_explained(variance_explained_noisy)