How to train raw image dataset for denoising

Thanks for your  excellent work!

I would like to train a raw image denoising model. what the data type I need to prepare? .raw? .dng?
And could this repo can train on raw/dng image? 
If possible.  Can you give me any guide to train raw/dng image~?

Thank you very much.
I will be grateful for any help you can provide!