'Construct a new L{SecondaryAuthority} from a tuple giving a server
address and a C{bytes} giving the name of a domain for which this is an
authority.
@param serverAddress: A two-tuple, the first element of which is a
C{str} giving an IP address and the second element of which is a
C{int} giving a port number.  Together, these define where zone
transfers will be attempted from.
@param domain: A C{bytes} giving the domain to transfer.
@return: A new instance of L{SecondaryAuthority}.'

@classmethod
def fromServerAddressAndDomain(cls, serverAddress, domain):

    secondary = cls(None, None)
    secondary.primary = serverAddress[0]
    secondary._port = serverAddress[1]
    secondary.domain = domain
    return secondary
