Storing a callback function as a class member

[Nathan Huesken]

Hey,

Sorry, I tried to sent only the relevant parts of the example, but the
part where the error was, was left out.

I defined the function, used as callback like this:
class SomeClass:
    def callback(param):
        ...

So I forgot the "self" parameter, and therefor the callback had a
different number of parameters than I expected.

Thanks for the effort!
Nathan