title: Replace a value in MultiIndex (pandas)
body: <p>In the following DataFrame: How can I replace <code>["x2", "Total"]</code> with <code>["x2", "x2"]</code> leaving <code>x1</code> as is?</p>
  
  <pre><code>l1           900    902    912     913    916     
  l2           ИП ПС  ИП ПС  ИП  ПС  ИП ПС  ИП ПС  
  i1    i2                                      
  x1    Total  10  6   3  3  10  16   2  9   3  8  
  x2    Total   1  0   0  0   0   0   0  0   0  0  
  </code></pre>
  
  <p><code>.rename</code> will replace all <code>"Total"</code> values, not just the one I need.</p>