title: Sort 3D array by specific dimension and element
body: <p>if I have a 3D array;
  such as:</p>
  
  <pre><code>[
    [
      [10,2],
      [5,3],
      [4,4]
    ],
    [
      [7,6],
      [4,2],
      [5,8]
    ]
  ] 
  </code></pre>
  
  <p>I want to sort them according to <strong>3rd dim &amp; 1st value.</strong></p>
  
  <p>It means, the result should be </p>
  
  <pre><code>[
    [
      [4,4],
      [5,3],
      [10,2]
    ],
    [
      [4,2],
      [5,8],
      [7,6]
    ]
  ]
  </code></pre>
  
  <p>How could I make it in python?</p>
  
  <p>Thx </p>