Remove model.trainer call inside of dataloading mixin (#7317)

* Update data_loading.py

* Update data_loading.py

Co-authored-by: Adrian Wälchli <[email protected]>

Author: ananthsub

pytorch_lightning/trainer/data_loading.py

@@ -17,7 +17,7 @@
 from abc import ABC
 from copy import deepcopy
 from functools import partial
-from typing import Any, Dict, Iterable, List, Optional, Tuple, Union
+from typing import Any, Callable, Dict, Iterable, List, Optional, Tuple, Union
 
 from torch.utils.data import BatchSampler, DataLoader, RandomSampler, SequentialSampler
 from torch.utils.data.distributed import DistributedSampler
@@ -56,6 +56,7 @@ class TrainerDataLoadingMixin(ABC):
     accelerator: Accelerator
     accelerator_connector: AcceleratorConnector
     dev_debugger: InternalDebugger
+    call_hook: Callable
 
     def _worker_check(self, dataloader: DataLoader, name: str) -> None:
         if not isinstance(dataloader, DataLoader):
@@ -437,8 +438,7 @@ def request_dataloader(self, model: LightningModule, stage: str) -> DataLoader:
         Returns:
             The dataloader
         """
-        if model.trainer is not None:
-            model.trainer.call_hook(f"on_{stage}_dataloader")
+        self.call_hook(f"on_{stage}_dataloader")
         dataloader: DataLoader = getattr(model, f'{stage}_dataloader')()
         dataloader = self._flatten_dl_only(dataloader)
         self.accelerator.barrier('get_dataloaders')