message: Fix MatplotlibDeprecationWarning: shading='flat' when X and Y have the same dimensions as C as it is deprecated since 3.3
diff: @@ -502,7 +502,7 @@ def plot_persistence_density(
  zi = k(np.vstack([xi.flatten(), yi.flatten()]))
  # Make the plot
  - img = axes.pcolormesh(xi, yi, zi.reshape(xi.shape), cmap=cmap)
  + img = axes.pcolormesh(xi, yi, zi.reshape(xi.shape), cmap=cmap, shading='auto')
  if greyblock:
  axes.add_patch(mpatches.Polygon([[birth.min(), birth.min()], [death.max(), birth.min()], [death.max(), death.max()]], fill=True, color='lightgrey'))
  