title: Finding indices of matches of one array in another array
body: <p>I have two numpy arrays, A and B. A conatains unique values and B is a sub-array of A.
  Now I am looking for a way to get the index of B's values within A.</p>
  
  <p>For example:</p>
  
  <pre><code>A = np.array([1,2,3,4,5,6,7,8,9,10])
  B = np.array([1,7,10])
  # I need a function fun() that:
  fun(A,B)
  &gt;&gt; 0,6,9
  </code></pre>