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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_app_auth_headers(self):
 """Set the correct auth headers to authenticate against GitHub."""

        now = datetime.now(timezone.utc)
        expiry = now + timedelta(minutes=5)

        data = {"iat": now, "exp": expiry, "iss": self.app_id}
        app_token = jwt.encode(data, self.app_key, algorithm="RS256").decode("utf-8")

        headers = {
            "Accept": PREVIEW_JSON_ACCEPT,
            "Authorization": "Bearer {}".format(app_token),
        }

        return headers