The simpler call to super(), without any arguments, will save you some typing in Python 3:

class CoolMixin(object):   
 
    def do_it(self):   
        return super(CoolMixin,    
                  self).do_it()   

class CoolMixin:

    def do_it(self):
        return super().do_it()

Specifying the class name and instance is optional, thereby making your code DRY and less prone to errors while refactoring.