Document exceptions in loggers (#6171)

* Document exceptions in loggers

* minor formatting

* docstring changed in comet.py

* Apply suggestions from code review

Co-authored-by: Rohit Gupta <rohitgr1998@gmail.com>

pytorch_lightning/loggers/comet.py

@@ -115,6 +115,12 @@ class CometLogger(LightningLoggerBase):
         prefix: A string to put at the beginning of metric keys.
         \**kwargs: Additional arguments like `workspace`, `log_code`, etc. used by
             :class:`CometExperiment` can be passed as keyword arguments in this logger.
+
+    Raises:
+        ImportError:
+            If required Comet package is not installed on the device.
+        MisconfigurationException:
+            If neither ``api_key`` nor ``save_dir`` are passed as arguments.
     """
 
     LOGGER_JOIN_CHAR = '-'

pytorch_lightning/loggers/mlflow.py

@@ -79,6 +79,9 @@ class MLFlowLogger(LightningLoggerBase):
             Has no effect if `tracking_uri` is provided.
         prefix: A string to put at the beginning of metric keys.
 
+    Raises:
+        ImportError:
+            If required MLFlow package is not installed on the device.
     """
 
     LOGGER_JOIN_CHAR = '-'

pytorch_lightning/loggers/neptune.py

@@ -171,6 +171,10 @@ class NeptuneLogger(LightningLoggerBase):
         prefix: A string to put at the beginning of metric keys.
         \**kwargs: Additional arguments like `params`, `tags`, `properties`, etc. used by
             :func:`neptune.Session.create_experiment` can be passed as keyword arguments in this logger.
+
+    Raises:
+        ImportError:
+            If required Neptune package is not installed on the device.
     """
 
     LOGGER_JOIN_CHAR = '-'

pytorch_lightning/loggers/test_tube.py

@@ -74,6 +74,10 @@ class TestTubeLogger(LightningLoggerBase):
             the user has defined the `self.example_input_array` attribute in their
             model.
         prefix: A string to put at the beginning of metric keys.
+
+    Raises:
+        ImportError:
+            If required TestTube package is not installed on the device.
     """
 
     __test__ = False

pytorch_lightning/loggers/wandb.py

@@ -61,6 +61,12 @@ class WandbLogger(LightningLoggerBase):
         \**kwargs: Additional arguments like `entity`, `group`, `tags`, etc. used by
             :func:`wandb.init` can be passed as keyword arguments in this logger.
 
+    Raises:
+        ImportError:
+            If required WandB package is not installed on the device.
+        MisconfigurationException:
+            If both ``log_model`` and ``offline``is set to ``True``.
+
     Example::
 
         from pytorch_lightning.loggers import WandbLogger