title: Remove rows in 3D numpy array
body: <p>I need to remove some rows from a 3D numpy array. For exampe:</p>
  
  <pre><code>a = [[1,2,3]
       [4,5,6]
       [7,8,9]
  
       [9,8,7]
       [6,5,4]
       [3,2,1]]
  </code></pre>
  
  <p>and I want to remove the third row of both pages of the matrix in order to obtain something like:</p>
  
  <pre><code> a = [[1,2,3]
       [4,5,6]
  
       [9,8,7]
       [6,5,4]]
  </code></pre>
  
  <p>I have tried with</p>
  
  <pre><code>   a = numpy.delete(a, 2, axis=0)
  </code></pre>
  
  <p>but I can't obtain what I need.</p>