'Checks if group is in cache. See `_get_state_for_groups`
Returns 2-tuple (`state_dict`, `got_all`). `got_all` is a bool
indicating if we successfully retrieved all requests state from the
cache, if False we need to query the DB for the missing state.
Args:
group: The state group to lookup'

def _get_all_state_from_cache(self, group):

    (is_all, _, state_dict_ids) = self._state_group_cache.get(group)
    return (state_dict_ids, is_all)
