Apply suggestions from code review

Author: Borda

tests/tests_pytorch/loops/test_double_iter_in_iterable_dataset.py

@@ -24,7 +24,7 @@
 import numpy as np
 from torch.utils.data import DataLoader, IterableDataset
 
-from lightning import Trainer
+from lightning.pytorch import Trainer
 from lightning.pytorch.demos.boring_classes import BoringModel