K-Fold Implementation with DataBlock

Can anyone please guide me that how we can implement K-fold Cross Validation in fastai.
Thank you so much.

Can I do 5-fold CV since data-set 80/20. I wan to separate data-set 80 into 4x20 and repeat with each 20 as validate and report the results and average values.
Can anyone please help me???
I truly appreciate your help.