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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def zero_mutable_fields(pkt, sending=False):
 """ When using AH, all "mutable" fields must be "zeroed" before calculating the ICV. See RFC 4302, Section 3.3.3.1. Handling Mutable Fields. @param pkt: an IP(v6) packet containing an AH layer. NOTE: The packet will be modified @param sending: if true, ipv6 routing headers will not be reordered """


    if pkt.haslayer(AH):
        pkt[AH].icv = chr(0) * len(pkt[AH].icv)
    else:
        raise TypeError('no AH layer found')

    if pkt.version == 4:
        # the tos field has been replaced by DSCP and ECN
        # Routers may rewrite the DS field as needed to provide a
        # desired local or end-to-end service
        pkt.tos = 0
        # an intermediate router might set the DF bit, even if the source
        # did not select it.
        pkt.flags = 0
        # changed en route as a normal course of processing by routers
        pkt.ttl = 0
        # will change if any of these other fields change
        pkt.chksum = 0

        immutable_opts = []
        for opt in pkt.options:
            if opt.option in IMMUTABLE_IPV4_OPTIONS:
                immutable_opts.append(opt)
            else:
                immutable_opts.append(Raw(chr(0) * len(opt)))
        pkt.options = immutable_opts

    else:
        # holds DSCP and ECN
        pkt.tc = 0
        # The flow label described in AHv1 was mutable, and in RFC 2460 [DH98]
        # was potentially mutable. To retain compatibility with existing AH
        # implementations, the flow label is not included in the ICV in AHv2.
        pkt.fl = 0
        # same as ttl
        pkt.hlim = 0

        next_hdr = pkt.payload

        while isinstance(next_hdr, (IPv6ExtHdrHopByHop, IPv6ExtHdrRouting, IPv6ExtHdrDestOpt)):
            if isinstance(next_hdr, (IPv6ExtHdrHopByHop, IPv6ExtHdrDestOpt)):
                for opt in next_hdr.options:
                    if opt.otype & 0x20:
                        # option data can change en-route and must be zeroed
                        opt.optdata = chr(0) * opt.optlen
            elif isinstance(next_hdr, IPv6ExtHdrRouting) and sending:
                # The sender must order the field so that it appears as it
                # will at the receiver, prior to performing the ICV computation.
                next_hdr.segleft = 0
                if next_hdr.addresses:
                    final = next_hdr.addresses.pop()
                    next_hdr.addresses.insert(0, pkt.dst)
                    pkt.dst = final
            else:
                break

            next_hdr = next_hdr.payload

    return pkt