fix mypy typing errors in lightning/trainer/optimizers.py (#13470)

Co-authored-by: Carlos Mocholí <[email protected]>

Author: gautierdag

pyproject.toml

@@ -86,7 +86,6 @@ module = [
     "pytorch_lightning.trainer.connectors.callback_connector",
     "pytorch_lightning.trainer.connectors.data_connector",
     "pytorch_lightning.trainer.data_loading",
-    "pytorch_lightning.trainer.optimizers",
     "pytorch_lightning.trainer.supporters",
     "pytorch_lightning.trainer.trainer",
     "pytorch_lightning.tuner.batch_size_scaling",

src/pytorch_lightning/trainer/optimizers.py

@@ -37,9 +37,10 @@ def init_optimizers(self, model: Optional["pl.LightningModule"]) -> Tuple[List,
             "`TrainerOptimizersMixin.init_optimizers` was deprecated in v1.6 and will be removed in v1.8."
         )
         pl_module = self.lightning_module or model
+        assert isinstance(pl_module, pl.LightningModule)
         return _init_optimizers_and_lr_schedulers(pl_module)
 
-    def convert_to_lightning_optimizers(self):
+    def convert_to_lightning_optimizers(self) -> None:
         r"""
         .. deprecated:: v1.6
             `TrainerOptimizersMixin.convert_to_lightning_optimizers` was deprecated in v1.6 and will be removed in v1.8.
@@ -59,6 +60,6 @@ def _convert_to_lightning_optimizer(optimizer: Optimizer) -> LightningOptimizer:
                     break
             return optimizer  # type: ignore [return-value]
 
-        self.strategy._cached_lightning_optimizers = {  # type: ignore [assignment]
+        self.strategy._cached_lightning_optimizers = {
             idx: _convert_to_lightning_optimizer(opt) for idx, opt in enumerate(self.optimizers)
         }