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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 should_add_ServerHello(self):
 """ Selecting a cipher suite should be no trouble as we already caught the None case previously. Also, we do not manage extensions at all. """

        if isinstance(self.mykey, PrivKeyRSA):
            kx = "RSA"
        elif isinstance(self.mykey, PrivKeyECDSA):
            kx = "ECDSA"
        usable_suites = get_usable_ciphersuites(self.cur_pkt.ciphers, kx)
        c = usable_suites[0]
        if self.preferred_ciphersuite in usable_suites:
            c = self.preferred_ciphersuite
        self.add_msg(TLSServerHello(cipher=c))
        raise self.ADDED_SERVERHELLO()