def import_preferred_memcache_lib(self, servers):
        try:
            import pylibmc
        except ImportError:
            pass
        else:
            return pylibmc.Client(servers)

        try:
            from google.appengine.api import memcache
        except ImportError:
            pass
        else:
            return memcache.Client()

        try:
            import memcache
        except ImportError:
            pass
        else:
            return memcache.Client(servers)


# backwards compatibility
Invalidates a used request token.
dataset/ETHPy150Open GoogleCloudPlatform/appengine-flask-skeleton/lib/werkzeug/contrib/cache.py/MemcachedCache.import_preferred_memcache_lib--crossover with--dataset/ETHPy150Open lepture/flask-oauthlib/flask_oauthlib/provider/oauth1.py/OAuth1RequestValidator.invalidate_request_token