remove isinstance Dataset check. test=develop (#40184)

python/paddle/fluid/dataloader/batch_sampler.py

@@ -113,8 +113,6 @@ class BatchSampler(Sampler):
             assert not shuffle, "shuffle should be False when sampler is set"
             self.sampler = sampler
         else:
-            assert isinstance(dataset, Dataset), \
-                "dataset should be a paddle.io.Dataset"
             assert not isinstance(dataset, IterableDataset), \
                 "dataset should not be a paddle.io.IterableDataset"
             assert sampler is None, \

python/paddle/fluid/reader.py

@@ -332,8 +332,6 @@ class DataLoader(object):
         self.use_buffer_reader = use_buffer_reader
         self.worker_init_fn = worker_init_fn
 
-        assert isinstance(dataset, Dataset), \
-            "dataset should be subclass instance of paddle.io.Dataset"
         self.dataset = dataset
 
         if not return_list and not in_dygraph_mode():