def map(self, callback, clients):
        for c in clients:
            if self.compare(c):
                callback(c)
Function to load a cache backend dynamically. This is flexible by design
dataset/ETHPy150Open qtile/qtile/libqtile/config.py/Match.map--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/django/core/cache/__init__.py/get_cache