stage-2 notebook says:
for i in range(20): row0 = i*250 row251 = row0+250 img = df.iloc[row0:row251, :] fig, ax = plt.subplots() plt.imshow(img, cmap='jet')
i think it should have been
row251 = row0+251
the plots should in the notebook has spiky boundary conditions at the edge which i think is wrong due to the bug.