Return packed byte representation of the UDP header.

def to_bytes(self, dochecksum=True):
        '''
        Return packed byte representation of the UDP header.
        '''
        csum = 0
        if dochecksum:
            csum = self.checksum()
        return b''.join((struct.pack(ICMP._PACKFMT, self._type.value, self._code.value, csum), self._icmpdata.to_bytes()))