human
Complete the below
@lru_cache(maxsize=None)
def cache_installed():

    ''''Returns ``True`` if a cache backend is configured, and the
    cache middleware classes or subclasses thereof are present.
    This will be evaluated once per run, and then cached.'
    '''
 Can you provide a the Python code you requested?
assistant
#Here is the Python code you requested.
    has_key = bool(getattr(settings, u'NEVERCACHE_KEY', u''))
    def flatten(seqs):
        return (item for seq in seqs for item in seq)
    middleware_classes = map(import_string, get_middleware_setting())
    middleware_ancestors = set(flatten(map(getmro, middleware_classes)))
    mezzanine_cache_middleware_classes = {import_string(u'mezzanine.core.middleware.UpdateCacheMiddleware'), import_string(u'mezzanine.core.middleware.FetchFromCacheMiddleware')}
    return (has_key and settings.CACHES and (not settings.TESTING) and mezzanine_cache_middleware_classes.issubset(middleware_ancestors))