title: How to delete a row based on a condition from a numpy array?
body: <p>From the following array :</p>
  
  <pre><code>test = np.array([[1,2,'a'],[4,5,6],[7,'a',9],[10,11,12]])
  </code></pre>
  
  <p>How can I delete the rows that contain 'a' ?
  Expected result :</p>
  
  <pre><code>array([[ 4,  5,  6],
     [10, 11, 12]])
  </code></pre>