Create the default version of the layer

        :return: a string of the packet with the payload

def do_build(self):
        """
        Create the default version of the layer

        :return: a string of the packet with the payload
        """
        if not self.explicit:
            self = next(iter(self))
        pkt = self.self_build()
        for t in self.post_transforms:
            pkt = t(pkt)
        pay = self.do_build_payload()
        if self.raw_packet_cache is None:
            return self.post_build(pkt, pay)
        else:
            return pkt + pay