Download FilletPlus - fillet one or several mesh corners 


This addon by zmj100 was adapted by me to be fully usable with bmesh,

Then I expanded on it and integrated it with multifillet:
you can now select any amount of edge corners to be filleted in one go.
Settings in Tools panel are self-explanatory.
As an added bonus, the face being filleted will not be erased but turned into an Ngon. Start of StatCounter Code for Default Guide