def add(self, alias: str, config: dict) -> None:
self._config[alias] = config<EOL>
Add a cache to the current config. If the key already exists, it
will overwrite it::

    >>> caches.add('default', {
            'cache': "aiocache.SimpleMemoryCache",
            'serializer': {
                'class': "aiocache.serializers.StringSerializer"
            }
        })

:param alias: The alias for the cache
:param config: Mapping containing the cache configuration