title: Generate new column based on column of dict?
body: <p>So I have a DataFrame like this</p>
  <pre><code>df = pd.DataFrame([
          [dict(F='y', G='v'),'F'],
          [dict(F='y', G='v'),'G'],
      ], columns=list('AB'))
  </code></pre>
  <p>I need to generate a new column C, based on column B and get sth like this</p>
  <pre><code>pd.DataFrame([
          [dict(F='y', G='v'),'F','y'],
          [dict(F='y', G='v'),'G','v'],
      ], columns=list('ABC'))
  </code></pre>
  <p>I am thinking of using apply function, but failed</p>