`validation_step` progress bar output should be used
When you're running validation steps your progress bar iter counter will increment once per validation_step. However, AFAICT there's no way to actually customize the progress_bar text during these validation_steps. For large validation sets, this makes it hard to know how far into validation you are, since the iter counter is the total steps.
I am returning a dict from validation_step like:
def validation_step(self, batch, batch_nb):
	output = {'progress_bar': {'batch_nb': batch_nb}}
	return output