diff --git a/doc/_gallery/plot_5_4_2_hough_noisy_chirp.py b/doc/_gallery/plot_5_4_2_hough_noisy_chirp.py
index 0c28fc3..d2f8377 100644
--- a/doc/_gallery/plot_5_4_2_hough_noisy_chirp.py
+++ b/doc/_gallery/plot_5_4_2_hough_noisy_chirp.py
@@ -22,8 +22,8 @@
 from tftb.generators import noisecg, sigmerge, fmlin
 from tftb.processing.cohen import WignerVilleDistribution
 from tftb.processing.postprocessing import hough_transform
-from mpl_toolkits.mplot3d import Axes3D
 import matplotlib.pyplot as plt
+from mpl_toolkits.mplot3d import Axes3D
 
 N = 64
 sig = sigmerge(fmlin(N, 0, 0.3)[0], noisecg(N), 1)