title: matplotlib: AttributeError: 'AxesSubplot' object has no attribute 'add_axes'
body: <p>Not sure exactly sure how to fix the following attribute error:</p>
  
  <pre><code>AttributeError: 'AxesSubplot' object has no attribute 'add_axes'
  </code></pre>
  
  <p>The offending problem seems to be linked to the way I have set up my plot:</p>
  
  <pre><code>gridspec_layout = gridspec.GridSpec(3,3)
  pyplot_2 = fig.add_subplot(gridspec_layout[2])
  
  ax = WCSAxes(fig, [0.1, 0.1, 0.8, 0.8], wcs=wcs)
  pyplot_2.add_axes(ax)
  </code></pre>
  
  <p>Does anybody know how to solve this? Many thanks.</p>