Class Inheritance - What am I doing wrong?

[Brian Munroe]

Ok, so thanks everyone for the helpful hints.  That *was* a typo on my
part (should've been super(B...) not super(A..), but I digress)

I'm building a public API.  Along with the API I have a few custom
types that I'm expecting API users to extend, if they need too.  If I
don't use name mangling, isn't that considered bad practice (read not
defensive programming) to not protect those 'private' fields?