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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 step2(self, atv_pub_key, atv_salt):
 """Second pairing step."""

        pk_str = binascii.hexlify(atv_pub_key).decode()
        salt = binascii.hexlify(atv_salt).decode()
        self._client_session_key, _, _ = self._session.process(pk_str, salt)

        if not self._session.verify_proof(self._session.key_proof_hash):
            raise exceptions.AuthenticationError('proofs do not match (mitm?)')

        pub_key = binascii.unhexlify(self._session.public)
        proof = binascii.unhexlify(self._session.key_proof)
        log_binary(_LOGGER, 'Client', Public=pub_key, Proof=proof)
        return pub_key, proof