question: New ModelCheckpoint Code Update Breaking Model Saving Functionality : v1.2.5->v.1.2.6
context: I am using Latest PT-Lightning and your upgrade to ModelCheckpoint broke my functionality to my codebase.
  V1.2.6 specifically coz I started facing these issues yesterday.  Downgraded to V1.2.5. Please check once. The dict based metrics returned from the train_step or validation_step are not captured in the ModelCheckpointCallback
   monitor_candidates = self._monitor_candidates(trainer)
  monitor_candidates doesn't have any values returned from the trainer. And I am not using the Result class. I am returning a pure dictionary.
  Didn't have time to create replicate the bug exactly in a notebook because I am on a tight deadline. But please do check.
  As I have more time, I will update more on the issue.
answer: You need to use self.log("your_metric", metric)
  And then set the monitor argument in ModelCheckpoint(monitor="your_metric")
  Let me know if that helps.