unattended-upgrades: ValueError: too many values to unpack (expected 2)

Using unattended-upgrades I want to update a Debian 12 system automatically. Since I have included some additional repositories, I need to configure apt pinning. If I include the following line of code in the /etc/apt/apt.conf.d/50unattended-upgradesConfig, the dry run fails because the label here has an unexpected = character inside l=source=none. How should it be escaped correctly? "o=cloudsmith/caddy/stable,a=${distro_codename},l=source=none,c=main"; **Dry Run** unattended-upgrades -d -v --dry-run --debug **Error Message** ValueError: too many values to unpack (expected 2)?