title: Pandas filter maximum groupby
body: <p>I have Pandas df:</p>
  
  <pre><code>family  age fruits
  ------------------
  Brown   12  7
  Brown   33  5
  Yellow  28  3
  Yellow  11  9
  </code></pre>
  
  <p>I want to get ages with next conditions:</p>
  
  <ol>
  <li>Group by family;</li>
  <li>Having maximum of fruits</li>
  </ol>
  
  <p>So result df will be:</p>
  
  <pre><code>family  age
  -----------
  Brown   12
  Yellow  11
  </code></pre>