title: How to monitor loss & val_loss at the same time to avoid overfitting Neural network to either train set or test set?
body: <p>I've been joining this hackathon and playing with keras callbacks and neural network, may I know if there is a way to monitor not only loss or val_loss but BOTH of them to avoid overfitting either the test or train set?
  e.g: can i put a function for the monitor field instead of just one field name?</p>
  <p>If I want to monitor val_loss to pick the lowest but I also want a second criteria to pick the minimum difference between val_loss and loss.</p>