diff --git a/pytorch_lightning/accelerators/accelerator.py b/pytorch_lightning/accelerators/accelerator.py
index 7087f6a261010..984f9a6842b4a 100644
--- a/pytorch_lightning/accelerators/accelerator.py
+++ b/pytorch_lightning/accelerators/accelerator.py
@@ -17,13 +17,14 @@
 from torch.optim import Optimizer
 
 from pytorch_lightning.core import LightningModule
-from pytorch_lightning.plugins.training_type import TrainingTypePlugin, HorovodPlugin
 from pytorch_lightning.plugins.precision import (
-    PrecisionPlugin,
-    MixedPrecisionPlugin,
     ApexMixedPrecisionPlugin,
+    MixedPrecisionPlugin,
     NativeMixedPrecisionPlugin,
+    PrecisionPlugin,
 )
+from pytorch_lightning.plugins.training_type import TrainingTypePlugin
+from pytorch_lightning.plugins.training_type.horovod import HorovodPlugin
 from pytorch_lightning.utilities.apply_func import move_data_to_device
 from pytorch_lightning.utilities.enums import AMPType, LightningEnum
 
@@ -374,4 +375,4 @@ def optimizer_state(self, optimizer: Optimizer) -> dict:
         return optimizer.state_dict()
 
     def on_save(self, checkpoint):
-        return checkpoint
\ No newline at end of file
+        return checkpoint
diff --git a/pytorch_lightning/plugins/training_type/training_type_plugin.py b/pytorch_lightning/plugins/training_type/training_type_plugin.py
index 349ed689254ad..5dbbf23881373 100644
--- a/pytorch_lightning/plugins/training_type/training_type_plugin.py
+++ b/pytorch_lightning/plugins/training_type/training_type_plugin.py
@@ -13,14 +13,16 @@
 # limitations under the License.
 import os
 from abc import ABC, abstractmethod
-from typing import Any, Optional, Sequence, Union
+from typing import Any, Optional, Sequence, TYPE_CHECKING, Union
 
 import torch
 
 from pytorch_lightning import _logger as log
 from pytorch_lightning.core.lightning import LightningModule
 from pytorch_lightning.plugins.base_plugin import Plugin
-from pytorch_lightning.trainer import Trainer
+
+if TYPE_CHECKING:
+    from pytorch_lightning.trainer.trainer import Trainer
 
 
 class TrainingTypePlugin(Plugin, ABC):
@@ -105,10 +107,10 @@ def results(self) -> Any:
     def rpc_enabled(self) -> bool:
         return False
 
-    def start_training(self, trainer: Trainer) -> None:
+    def start_training(self, trainer: 'Trainer') -> None:
         # double dispatch to initiate the training loop
         self._results = trainer.train()
 
-    def start_testing(self, trainer: Trainer) -> None:
+    def start_testing(self, trainer: 'Trainer') -> None:
         # double dispatch to initiate the test loop
         self._results = trainer.run_test()
diff --git a/setup.cfg b/setup.cfg
index deccd35af8f98..ee23dd130de10 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -142,7 +142,7 @@ ignore_errors = True
 ignore_errors = True
 
 # todo: add proper typing to this module...
-[mypy-pytorch_lightning.accelerators.legacy.*]
+[mypy-pytorch_lightning.accelerators.*]
 ignore_errors = True
 
 # todo: add proper typing to this module...