title: Pandas: getting rid of the multiindex
body: <p>After grouping and counting a dataframe I'm trying to remove the multiindex like this:</p>
  <pre><code>df = df[['CID','FE', 'FID']].groupby(by=['CID','FE']).count()
                .unstack().reset_index()
  </code></pre>
  <p>Printing the columns (<code>df.colums</code>) shows that it is still a <code>MultiIndex</code>.</p>
  <pre><code>MultiIndex(levels=[['FID', 'CID'], [...]]
  </code></pre>
  <p>I can't access the column <code>CID</code> via <code>df['CID']</code>.</p>