title: finding index of none and nan in numpy array
body: <p>I have an array which looks like:</p>
  
  <pre><code>array([[  1.,   2.,   None],
         [ nan,   4.,   5.]])
  </code></pre>
  
  <p>I am trying the following:</p>
  
  <pre><code>np.equal(A, None) #works and finds index of None correctly
  np.equal(A, np.nan) #doesn't work
  np.isnan(A) #errors out
  </code></pre>
  
  <p>The error is:</p>
  
  <pre><code>TypeError: ufunc 'isnan' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''
  </code></pre>
  
  <p>How should I approach this, I am trying to find the index of None and nan in a given array.</p>
  
  <p>My final output should look as:</p>
  
  <pre><code>array([[False, False,  True],
         [True, False, False]], dtype=bool)
  </code></pre>