title: how to reshape 3D to 2D ? but I don't want to lose the brackets in between?
body: <p>I have this array</p>
  <pre><code>X = np.array([[-2, -1.9], [-3, -2], [-1, -1],  [1, 1.5], [3, 2]])
  </code></pre>
  <p>once I insert a point</p>
  <pre><code>x = np.asarray([[20, 4.9]]) 
  </code></pre>
  <p>it becomes 3D</p>
  <pre><code>array([[[-2. , -1.9],
          [-3. , -2. ],
          [-1. , -1. ],
          [ 1. ,  1.5],
          [ 3. ,  2. ],
          [20. ,  4.9]]])
  </code></pre>
  <p>How to keep it always 2D even if I added points ?</p>