RPython cannot handle @property
RPython cannot use super and doesn't handle mutlipe inheritance

The _mixin_ = True however allows us kind-of multiple-inheritances. Be caucious, tho
RPython does not like mixin of pointers (eg, None) and ints/booleans
str.startswith only takes one arg (+self) in rpython
RPython can't deal with tuples of different sized passed to the same function

RPython does see them as distinct, incompatible types.
The lists used now are immutable, nevertheless.
RPython does not like file object

We use file as stream from the rlib.
RPython chokes on dicts with values of different types

this is a problem in the case when we want to "as_str" the pseudo-enum
. So we just filter the int-value part of the dict and, as a small optimization
use a translate-time unrolling of the if-switch.
RPython cannot use the print-function yet
RPython cannot assure that the return of get_instance_invokable is not None

so we assist it that this is indeed the case;
byte-arrays cannot be made using array() in RPython
RPython cannot create closures dynamically

hence, we make _invoke readily availabe. Also, is_empty is now state-based
and not behavior-based
nits: trailing spaces
we cannot use the stdlib os.path.split* so we do our own
Add target file and rework system exit

RPython does not like sys.exit, so we emulate it using an Exit-Exception.
Also, we add a proper target file