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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 ParseIfaddrs(ifaddrs):
 """Parses contents of the intrusive linked list of `ifaddrs`. Args: ifaddrs: A pointer to the first node of `ifaddrs` linked list. Can be NULL. Returns: An iterator over instances of `rdf_client_network.Interface`. """

  precondition.AssertOptionalType(ifaddrs, ctypes.POINTER(Ifaddrs))

  ifaces = {}

  for ifaddr in IterIfaddrs(ifaddrs):
    ifname = ctypes.string_at(ifaddr.ifa_name).decode("utf-8")
    iface = ifaces.setdefault(ifname, rdf_client_network.Interface())
    iface.ifname = ifname

    if not ifaddr.ifa_addr:
      continue

    sockaddr = ctypes.cast(ifaddr.ifa_addr, ctypes.POINTER(Sockaddr))
    iffamily = sockaddr.contents.sa_family
    if iffamily == AF_INET:
      sockaddrin = ctypes.cast(ifaddr.ifa_addr, ctypes.POINTER(Sockaddrin))

      address = rdf_client_network.NetworkAddress()
      address.address_type = rdf_client_network.NetworkAddress.Family.INET
      address.packed_bytes = struct.pack("=L", sockaddrin.contents.sin_addr)
      iface.addresses.append(address)
    elif iffamily == AF_INET6:
      sockaddrin = ctypes.cast(ifaddr.ifa_addr, ctypes.POINTER(Sockaddrin6))

      address = rdf_client_network.NetworkAddress()
      address.address_type = rdf_client_network.NetworkAddress.Family.INET6
      address.packed_bytes = bytes(list(sockaddrin.contents.sin6_addr))
      iface.addresses.append(address)
    elif iffamily == AF_LINK:
      sockaddrdl = ctypes.cast(ifaddr.ifa_addr, ctypes.POINTER(Sockaddrdl))

      nlen = sockaddrdl.contents.sdl_nlen
      alen = sockaddrdl.contents.sdl_alen
      iface.mac_address = bytes(sockaddrdl.contents.sdl_data[nlen:nlen + alen])
    else:
      raise ValueError("Unexpected socket address family: %s" % iffamily)

  return itervalues(ifaces)