title: Plot secondary axis on multiple subplots in python
body: <p>I am trying to plot on the secondary axis of all subplots of a bar chart, but I was only successful showing the secondary plot on one of the subplots (see image below). 
  I tried: </p>
  
  <pre><code>df[['loan_amnt','int_rate']].plot(kind='bar',subplots=True,layout=(1,2), figsize=(15,5))
  df['dti'].plot(secondary_y=True, marker='d', style='g:');
  </code></pre>
  
  <p>and got see below:</p>
  
  <p><a href="https://i.stack.imgur.com/dCGET.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dCGET.png" alt="enter image description here"></a>
  What can I add to this code to ensure that the secondary plot is displayed on both subplots.</p>