Converts Interface to ExportedNetworkInterfaces.

def Convert(self, metadata, interface, token=None):
    """Converts Interface to ExportedNetworkInterfaces."""
    ip4_addresses = []
    ip6_addresses = []
    for addr in interface.addresses:
      if addr.address_type == addr.Family.INET:
        ip4_addresses.append(addr.human_readable_address)
      elif addr.address_type == addr.Family.INET6:
        ip6_addresses.append(addr.human_readable_address)
      else:
        raise ValueError("Invalid address type: %s" % addr.address_type)

    result = ExportedNetworkInterface(
        metadata=metadata,
        ifname=interface.ifname,
        ip4_addresses=" ".join(ip4_addresses),
        ip6_addresses=" ".join(ip6_addresses))

    if interface.mac_address:
      result.mac_address = interface.mac_address.human_readable_address

    yield result