Add docstrings in mlflow logger class (#9030)

Co-authored-by: Ethan Harris <[email protected]>

Author: bamblebam

pytorch_lightning/loggers/mlflow.py

@@ -171,14 +171,24 @@ def experiment(self) -> MlflowClient:
         return self._mlflow_client
 
     @property
-    def run_id(self):
-        # create the experiment if it does not exist to get the run id
+    def run_id(self) -> str:
+        """
+        Create the experiment if it does not exist to get the run id.
+
+        Returns:
+            The run id.
+        """
         _ = self.experiment
         return self._run_id
 
     @property
-    def experiment_id(self):
-        # create the experiment if it does not exist to get the experiment id
+    def experiment_id(self) -> str:
+        """
+        Create the experiment if it does not exist to get the experiment id.
+
+        Returns:
+            The experiment id.
+        """
         _ = self.experiment
         return self._experiment_id
 
@@ -239,8 +249,20 @@ def save_dir(self) -> Optional[str]:
 
     @property
     def name(self) -> str:
+        """
+        Get the experiment id.
+
+        Returns:
+            The experiment id.
+        """
         return self.experiment_id
 
     @property
     def version(self) -> str:
+        """
+        Get the run id.
+
+        Returns:
+            The run id.
+        """
         return self.run_id