STYLE: Fix lightning deprecation warnings

I'm fixing a few issues that would prevent upgrading the pytorch-lightning package. Trainer.lr_schedulers is being replaced with trainer.lr_scheduler_configs. In future versions, using trainer.logger with multiple loggers will only return the first logger available, so I'm iterating through trainer.loggers instead. And LightningLoggerBase.close is being replaced with LightningLoggerBase.finalize.

Closes #751

InnerEye/ML/lightning_base.py

@@ -395,5 +395,5 @@ class InnerEyeLightning(LightningModule):
         assert isinstance(self.trainer, Trainer)
         self.log_on_epoch(MetricType.LOSS, loss, is_training)
         if is_training:
-            learning_rate = self.trainer.lr_schedulers[0]['scheduler'].get_last_lr()[0]
+            learning_rate = self.trainer.lr_scheduler_configs[0].scheduler.get_last_lr()[0]  # type: ignore
             self.log_on_epoch(MetricType.LEARNING_RATE, learning_rate, is_training)

InnerEye/ML/model_training.py

@@ -266,7 +266,8 @@ def model_train(checkpoint_path: Optional[Path],
     logging.info("Starting training")
 
     trainer.fit(lightning_model, datamodule=data_module)
-    trainer.logger.close()  # type: ignore
+    for logger in trainer.loggers:
+        logger.finalize("success")
 
     world_size = getattr(trainer, "world_size", 0)
     is_azureml_run = not is_offline_run_context(RUN_CONTEXT)