Dynamically add class method causes "SystemError: ... bad argument to internal function"

[Newgene]

I have noticed that the exception was caused by the call of "self.f()"
within my "_generic" function. It will raise SystemError exception
whenever I refer to any method or attribute of "self" within "_generic"
function. Otherwise, dynamically adding method works fine. I cannot
figure out what's the reason there.

CW