title: How can I modify ModelCheckPoint in keras to monitor both val_acc and val_loss and save accordingly the best model?
body: <p><code>ModelCheckPoint</code> gives options to save both for <code>val_Acc</code> and <code>val_loss</code> separately. 
  I want to modify this in a way so that if <code>val_acc</code> is improving -> save model. if <code>val_acc</code> is equal to previous best <code>val_acc</code> then check for <code>val_loss</code>, if <code>val_loss</code> is less than previous best <code>val_loss</code> then save the model.</p>
  
  <pre><code>    if val_acc(epoch i)&gt; best_val_acc:
          save model
      else if val_acc(epoch i) == best_val_acc:
          if val_loss(epoch i) &lt; best_val_loss:
             save model
          else
             do not save model
  </code></pre>