# Before sending to the model, ``collate_fn`` function works on a batch of samples generated from ``DataLoader``. The input to ``collate_fn`` is a batch of data with the batch size in ``DataLoader``, and ``collate_fn`` processes them according to the data processing pipelines declared previously. Pay attention here and make sure that ``collate_fn`` is declared as a top level def. This ensures that the function is available in each worker.
