<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def count(cls, slug):
 """get the number of objects in the cache for a given slug :param slug: cache key :return: `int` """

        from .models import Content
        # Gets the count for a tag, hopefully form an in-memory cache.
        cnt = cls._cache.get(slug)
        if cnt is None:
            cnt = Content.search_objects.search(tags=[slug]).count()
            cls._cache[slug] = cnt
        return cnt