'Roll back reservations.
:param context: The request context, for access checks.
:param reservations: A list of the reservation UUIDs, as
returned by the reserve() method.
:param project_id: Specify the project_id if current context
is admin and admin wants to impact on
common user\'s tenant.
:param user_id: Specify the user_id if current context
is admin and admin wants to impact on
common user.'

def rollback(self, context, reservations, project_id=None, user_id=None):

    pass
