def new_instance(before=None):
    """
        Create a new object to be used concurrently.

        If *before* is given, it is an integer TID, giving the *maximum*
        transaction that will be visible to this object (this only works
        correctly for history-preserving storages).

        .. caution::

           Failing to provide *before* for a historical connection
           will lead to consistency errors.
        """
