Forces a refresh of a cached item.

        :param item: Client name.
        :type item: unicode | str
        :return: Items in the cache.
        :rtype: DockerHostItemCache.item_class

def refresh(self, item):
        """
        Forces a refresh of a cached item.

        :param item: Client name.
        :type item: unicode | str
        :return: Items in the cache.
        :rtype: DockerHostItemCache.item_class
        """
        client = self._clients[item].get_client()
        self[item] = val = self.item_class(client)
        return val