abstractmethod

A decorator indicating abstract methods.

Requires that the metaclass is ABCMeta or derived from it.  A
class that has a metaclass derived from ABCMeta cannot be
instantiated unless all of its abstract methods are overridden.
The abstract methods can be called using any of the normal
'super' call mechanisms.  abstractmethod() may be used to declare
abstract methods for properties and descriptors.

Usage:

    class C(metaclass=ABCMeta):
        @abstractmethod
        def my_abstract_method(self, arg1, arg2, argN):
            ...