Problem plotting convex hull of random points

Question

Something that escapes me...

When I run the first program below in a Jupyter notebook:

import numpy as np
from numpy import random
from scipy.spatial import ConvexHull
import matplotlib.pyplot as plt

points = np.random.rand(30, 2)

hull = ConvexHull(points)

plt.plot(points[:,0], points[:,1], 'o')

for simplex in hull.simplices:
    plt.plot(points[simplex,0], points[simplex,1], 'k-')

I get, as expected, a plot of points and convex hull:

And when, after that, I run the second program below:

import numpy as np
from numpy import random
from scipy.spatial import ConvexHull, convex_hull_plot_2d

points = np.random.rand(30, 2)

hull = ConvexHull(points)

convex_hull_plot_2d(hull)

I get a double plot !

What am I missing?