title: Pandas drop_duplicates method not working on dataframe containing lists
body: <p>I am trying to use drop_duplicates method on my dataframe, but I am getting an 
  error. See the following:</p>
  
  <blockquote>
    <p>error: TypeError: unhashable type: 'list'</p>
  </blockquote>
  
  <p>The code I am using:</p>
  
  <pre><code>df = db.drop_duplicates()
  </code></pre>
  
  <p>My DB is huge and contains strings, floats, dates, NaN's, booleans, integers... Any help is appreciated.</p>