title: How to select rows with more than one value in Pandas DataFrame
body: <p>I have a DataFrame that looks like this:</p>
  <pre><code>    Entry   ribosome protein    PDB
  0   P46782            s5         4ug0;4v6x;5a2q;5aj0;5flx;5lks;5oa3;5t2c;5vyc;6...
  1   P0A7W3            s5         5wf0;5wfs;6awb;6awc;6awd
  2   A2RNN6            s5         5myj
  3   Q5SHQ5            s5         1fjg;1fka;1hnw;1hnx;1hnz;1hr0;1i94;1i95;1i96;1...
  4   Q2YYL4            s5         6fxc
  5   A0QSG6            s5         5o5j;5o61;5xyu;5zeb;5zep;5zeu;6dzi;6dzk
  6   P33759            s5         5mrc;5mre;5mrf`
  </code></pre>
  <p>I need to extract rows that have more than one entry in a column 'PDB'.
  For example, I want to have the DataFrame that shows rows without &quot;6fxc&quot; and &quot;5myj&quot; (single entries) in this case, but only multiple PDBs like &quot;5mrc;5mre;5mrf&quot;.</p>
  <p>How to do it?</p>
  <p>This is only a fragment of a huge dataframe with such data, that I need to filter this way.</p>