为什么代码中我们只想要"返回r [Ether] .src"时，循环语句是"for s，r in responses"而不是"for r in responses"？

Question

还有，为什么我们有“responses，unanswered=”而不是“responses=”in“responses，unanswered=srp（以太（dst=“ff:ff:ff:ff:ff”）/ARP（pdst=ip\u地址），timeout=2，retry=10）”响应和未响应都是什么

    from scapy.all import *
    import sys
    import threading

    interface = "eth0"
    target_ip = "172.16.155.137"
    gateway_ip = "172.16.155.2"
    packet_count = 100000
    poisoning = True

    def restore_target(gateway_ip, gateway_mac, target_ip, target_mac):

        print "[*] Restoring target..."
        send(ARP(op=2, psrc=gateway_ip, pdst=target_ip, hwdst="ff:ff:ff:ff:ff:ff", hwsrc=gateway_mac), count=5)
        send(ARP(op=2, psrc=target_ip, pdst=gateway_ip, hwdst="ff:ff:ff:ff:ff:ff",
             hwsrc=target_mac), count=5)

    def get_mac(ip_address):
        responses,unanswered = srp(Ether(dst="ff:ff:ff:ff:ff:ff")/ARP(pdst=ip_address),timeout=2,retry=10)

        # return the MAC address from a response
        for s, r in responses:
            return r[Ether].src

       return None