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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 register_pubkey(self):
 """ XXX Check that the pubkey received is in the group. """

        p = pkcs_os2ip(self.dh_p)
        g = pkcs_os2ip(self.dh_g)
        pn = dh.DHParameterNumbers(p, g)

        y = pkcs_os2ip(self.dh_Ys)
        public_numbers = dh.DHPublicNumbers(y, pn)

        s = self.tls_session
        s.server_kx_pubkey = public_numbers.public_key(default_backend())

        if not s.client_kx_ffdh_params:
            s.client_kx_ffdh_params = pn.parameters(default_backend())