docs: def visualize_poisson_w(w, labels, filename, method='pca', figsize=(18,10), title='', **scatter_options):
      """
      Saves a scatter plot of a visualization of W, the result from Poisson SE.
      """
      if method == 'pca':
          pca = PCA(2)
          r_dim_red = pca.fit_transform(w.T).T
      elif method == 'tsne':
          pass
      else:
          print("Method is not available. use 'pca' (default) or 'tsne'.")
          return
      visualize_dim_red(r_dim_red, labels, filename, figsize, title, **scatter_options)