title: Test if numpy array contains only zeros
body: <p>We initialize a numpy array with zeros as bellow:</p>
  
  <pre><code>np.zeros((N,N+1))
  </code></pre>
  
  <p>But how do we check whether all elements in a given n*n numpy array matrix is zero.<br>
  The method just need to return a True if all the values are indeed zero.</p>