code: def rollback(self, sql=None):
          
          self._transaction = False
          try:
              rollback = self._con.rollback
          except AttributeError:
              return self._con.query(sql or 'rollback')
          else:
              if sql:
                  return rollback(sql=sql)
              else:
                  return rollback()
docs: Rollback the current transaction.