title: Wrong picture ploted with matplotlib 3d in jupyter lab
body: <p>I want to draw 3D graphics in jupyter lab with matplotlib, but it does not draw correct graphs.</p>
  
  <p>jupyter lab, run in kubernetes container, with python 3.</p>
  
  <pre class="lang-py prettyprint-override"><code>import numpy as np
  import matplotlib.pyplot as plt
  from mpl_toolkits.mplot3d import Axes3D
  
  x = np.linspace(-6 * np.pi,6 * np.pi,1000)
  y = np.sin(x)
  z = np.cos(x)
  
  fig = plt.figure()
  ax = Axes3D(fig)
  ax.plot(x, y, z)
  </code></pre>
  
  <p><a href="https://i.loli.net/2019/07/10/5d25ba2208da997816.png" rel="nofollow noreferrer">the output is like this:</a></p>
  
  <p>Can not find the reason currently, any help is appreciated, thanks.</p>