Effectively retrieve data according to lazy_collection.
        If we have a stored collection, without any result, return an empty list

def _collection(self):
        """
        Effectively retrieve data according to lazy_collection.
        If we have a stored collection, without any result, return an empty list
        """
        old_sort_limits_and_len_mode = None if self._sort_limits is None else self._sort_limits.copy(), self._len_mode
        old_sorts = None if self._sort is None else self._sort.copy(),\
                    None if self._sort_by_sortedset is None else self._sort_by_sortedset.copy()
        try:
            if self.stored_key and not self._stored_len:
                if self._len_mode:
                    self._len = 0
                    self._len_mode = False
                self._sort_limits = {}
                return []

            # Manage sort desc added by original `__getitem__` when we sort by score
            if self._sort_by_sortedset and self._sort and self._sort.get('desc'):
                self._sort = None
                self._sort_by_sortedset['desc'] = not self._sort_by_sortedset.get('desc', False)

            return super(ExtendedCollectionManager, self)._collection
        finally:
            self._sort_limits, self._len_mode = old_sort_limits_and_len_mode
            self._sort, self._sort_by_sortedset = old_sorts