title: NumPy boolean array warning?
body: <p>I have a few numpy arrays, lets say <code>a</code>, <code>b</code>, and <code>c</code>, and have created a <code>mask</code> to apply to all of them. </p>
  
  <p>I am trying to mask them as such:</p>
  
  <p><code>a = a[mask]</code></p>
  
  <p>where <code>mask</code> is a <code>bool</code> array. It is worth noting that I have verified that</p>
  
  <p><code>len(a) = len(b) = len(c) = len(mask)</code></p>
  
  <p>And I am getting a rather cryptic sounding warning:</p>
  
  <p><code>FutureWarning: in the future, boolean array-likes will be handled as a boolean array index</code></p>