'Rollback the current transaction in progress.
If no transaction is in progress, this method is a pass-through.
This method rolls back the current transaction or nested transaction
regardless of subtransactions being in effect.  All subtransactions up
to the first real transaction are closed.  Subtransactions occur when
begin() is called multiple times.
.. seealso::
:ref:`session_rollback`'

def rollback(self):

    if (self.transaction is None):
        pass
    else:
        self.transaction.rollback()
