Pin_memory: True in config causes error.

[sesevgen]

Describe the bug
Setting pin_memory: True in yaml under dataloader causes an AttributeError:
"AttributeError: 'dict' object has no attribute 'cuda'"

To Reproduce
Steps to reproduce the behavior:
Set in a configuration file:
training:
dataloader:
pin_memory:True

and run with GPU enabled.

Desktop (please complete the following information):

• OS: Ubuntu 16.04.5 LTS (Newton)
• Python version 3.6
• PyTorch version 4.1

[sesevgen]

This can be fixed by adding an explicit conversion from dict to DataDict on line 613 of worker.py, but that shouldn't be necessary. It should be DataDict type in the first place.