--load-existing cannot be set to False, which I need to skip confirmation

[eatwithforks]

sfn ... --load-existing false
ERROR: Invalid type for `load_existing` (false <String>). Valid - TrueClass,FalseClass,NilClass,NilClass

I also tried the maybe supported --no-load-existing, but that did not work either.
I think the solution would be to add a custom parser as: -> {} that returns false when the string false was passed ... does this sound correct, would you accept a PR for that ?