Generate the stack suffix. A stack suffix can be used as the key to a SimRun in CFG recovery.

        :param int context_sensitivity_level: Level of context sensitivity.
        :return: A tuple of stack suffix.
        :rtype: tuple

def stack_suffix(self, context_sensitivity_level):
        """
        Generate the stack suffix. A stack suffix can be used as the key to a SimRun in CFG recovery.

        :param int context_sensitivity_level: Level of context sensitivity.
        :return: A tuple of stack suffix.
        :rtype: tuple
        """

        ret = ()

        for frame in self:
            if len(ret) >= context_sensitivity_level*2:
                break
            ret = (frame.call_site_addr, frame.func_addr) + ret

        while len(ret) < context_sensitivity_level*2:
            ret = (None, None) + ret

        return ret