'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):

    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
