title: Pandas drop duplicates if reverse is present between two columns
body: <p>I have a dataset with 2 columns like the following...</p>
  
  <pre><code>InteractorA InteractorB
  AGAP028204  AGAP005846
  AGAP028204  AGAP003428
  AGAP028200  AGAP011124
  AGAP028200  AGAP004335
  AGAP028200  AGAP011356
  AGAP028194  AGAP008414
  </code></pre>
  
  <p>I'm using Pandas and I want to drop rows which are present twice but simply reversed like the following... from this...</p>
  
  <pre><code>InteractorA InteractorB
  AGAP002741  AGAP008026
  AGAP008026  AGAP002741
  </code></pre>
  
  <p>To this...</p>
  
  <pre><code>InteractorA InteractorB
  AGAP002741  AGAP008026
  </code></pre>
  
  <p>As they are for all intents and purposes the same thing.</p>
  
  <p>Is there a built in method to handle this?</p>