Cloudflare Clef joint schema reference implementation

Source: https://huggingface.co/Cloudflare/clef-flash/blob/17f0b0ad64efb65d273590632833508766b2aae6/joint_schema_model.py
The same source file is used by Cloudflare/clef at revision
2f3de3dd85f379784083b0814d997ab627200f0c.
SHA-256: 0e304cf7c6500e8bb59bef7e2afd2c6373f82596dfb3b57d1aa93c175e2dc3a3
The vendored file is unmodified. The accompanying LICENSE is Apache-2.0.
