Finalizes the request.

def _finalize(self):
        """
        Finalizes the request.
        """
        if len(self.all_successors) == 0:
            return

        # do some cleanup
        if o.DOWNSIZE_Z3 in self.all_successors[0].options:
            for s in self.all_successors:
                s.downsize()

        # record if the exit is unavoidable
        if len(self.flat_successors) == 1 and len(self.unconstrained_successors) == 0:
            self.flat_successors[0].scratch.avoidable = False