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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 _get_subject_public_key(cert):
 """ Returns the SubjectPublicKey asn.1 field of the SubjectPublicKeyInfo field of the server's certificate. This is used in the server verification steps to thwart MitM attacks. :param cert: X509 certificate from pyOpenSSL .get_peer_certificate() :return: byte string of the asn.1 DER encoded SubjectPublicKey field """

        public_key = cert.get_pubkey()
        cryptographic_key = public_key.to_cryptography_key()
        subject_public_key = cryptographic_key.public_bytes(Encoding.DER,
                                                            PublicFormat.PKCS1)
        return subject_public_key