Document exceptions in accelerators (#9558)

* Document exceptions in ipu.py

* Document exceptions in tpu.py

* Document exceptions in gpu.py

pytorch_lightning/accelerators/gpu.py

@@ -27,17 +27,17 @@ class GPUAccelerator(Accelerator):
     """Accelerator for GPU devices."""
 
     def setup_environment(self) -> None:
+        """
+        Raises:
+            MisconfigurationException:
+                If the selected device is not GPU.
+        """
         super().setup_environment()
         if "cuda" not in str(self.root_device):
             raise MisconfigurationException(f"Device should be GPU, got {self.root_device} instead")
         torch.cuda.set_device(self.root_device)
 
     def setup(self, trainer: "pl.Trainer") -> None:
-        """
-        Raises:
-            MisconfigurationException:
-                If the selected device is not GPU.
-        """
         self.set_nvidia_flags(trainer.local_rank)
         return super().setup(trainer)
 

pytorch_lightning/accelerators/ipu.py

@@ -24,6 +24,11 @@ class IPUAccelerator(Accelerator):
     """Accelerator for IPUs."""
 
     def setup_optimizers(self, trainer: "pl.Trainer") -> None:
+        """
+        Raises:
+            MisconfigurationException:
+                If multiple optimizers are provided.
+        """
         super().setup_optimizers(trainer)
 
         if len(self.optimizers) > 1:

pytorch_lightning/accelerators/tpu.py

@@ -36,7 +36,9 @@ class TPUAccelerator(Accelerator):
         """
         Raises:
             MisconfigurationException:
-                If AMP is used with TPU, or if TPUs are not using a single TPU core or TPU spawn training.
+                If AMP is used with TPU.
+            MisconfigurationException:
+                If TPUs are not using a single TPU core or TPU spawn training.
         """
         if isinstance(self.precision_plugin, MixedPrecisionPlugin):
             raise MisconfigurationException(