title: Filtering Pandas DataFrame by value in a column's lists
body: <p>I have a DataFrame that has a column of lists. I would like to return a subset of the Dataframe of those rows whose list contains a specified value.</p>
  <pre><code>test = pd.DataFrame({'detail_id': [10000, 10001, 10002], 
                       'tokens': [['A', 'B', 'C'], ['A', 'D'], ['C', 'E', 'F', 'H']]})
  </code></pre>
  <p>If I filter by for a particular ID this way it works</p>
  <pre><code>test[test['detail_id'] == 10001]
  </code></pre>
  <p>If I just want the first 2 rows that have 'A' in their tokens lists, the following does not work</p>
  <pre><code>test['A' in test['tokens']]
  </code></pre>
  <p>I get a <code>KeyError: False</code>. I understand why, but I'm struggling to figure out a solution. Suggestions?</p>