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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 sign_certificate():
 """ Get the new certificate. Returns the signed bytes. """

    LOGGER.info("Signing certificate...")
    cmd = [
        'openssl', 'req',
        '-in', os.path.join(gettempdir(), 'domain.csr'),
        '-outform', 'DER'
    ]
    devnull = open(os.devnull, 'wb')
    csr_der = subprocess.check_output(cmd, stderr=devnull)
    code, result = _send_signed_request(DEFAULT_CA + "/acme/new-cert", {
        "resource": "new-cert",
        "csr": _b64(csr_der),
    })
    if code != 201:
        raise ValueError("Error signing certificate: {0} {1}".format(code, result))
    LOGGER.info("Certificate signed!")

    return result