Make `trainer` class check less restrictive

Summary:
Pull Request resolved: https://github.com/facebookresearch/d2go/pull/508

Avoid unnecessary restriction to base class Trainer. Subclasses of `SimpleTrainer` would work as well.

Reviewed By: wat3rBro

Differential Revision: D44221069

fbshipit-source-id: a666977b2073b4525b4c6940c121f6b05466e5d7

d2go/quantization/modeling.py

@@ -665,8 +665,11 @@ def _reset_qat_data_loader_if_needed(cfg, trainer, build_loader_func):
                 old_bs, new_bs
             )
         )
-        # This method assumes the data loader can be replaced from trainer
-        assert trainer.__class__ == SimpleTrainer
+
+        assert isinstance(
+            trainer, SimpleTrainer
+        ), "Trainer needs to be a subclass of SimpleTrainer to support resetting the dataloader"
+
         trainer.reset_data_loader(lambda: build_loader_func(loader_cfg))