title: Pandas select row by condition and drop all others who don't comply
body: <p>I have a <code>DataFrame</code>:</p>
  <pre><code>id_1  |   value
  
   1          6
   1          5
   1          2
   2          1
   3          2
   3          4
  ...        ...
   
  </code></pre>
  <p>I wish to remove the duplicates of <code>id_1</code> so that there would be distinct id's. I want that the row that contains the higher value will remain.</p>
  <p>output:</p>
  <pre><code>id_1  |   value
  
   1          6
   2          1
   3          4
  ...        ...
  </code></pre>
  <p>It's quite straightforward to solve when iterating over the rows. But is there a way to do it without using a for loop?</p>