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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 import_rsa_key(pem_data):
 """ Extract an RSA key from a PEM-encoded X.509 certificate :param pem_data: RSA key encoded in standard form :return: rsa.RSAPublicKey instance """

    if not pem_data.startswith(PREFIX):
        pem_data = bytes('{}\n{}\n{}'.format(PREFIX, pem_data, POSTFIX),
                         'utf-8')
    else:
        pem_data = bytes(pem_data, 'utf-8')
    cert = x509.load_pem_x509_certificate(pem_data, default_backend())
    return cert.public_key()