Calibrating Hull-White with negative interest rates


Hi All

I have seen a couple of topics regarding this, but the problem is that the function BermudanSwaption uses a lognormal which obviously cannot be used on negative interest rates.

Is there a way to change this? (I can see it uses a UseMethod from Python I think?) or is there another work around - for example by shifting the numbers to positive?

Thanks in advance.

Kind regards,