Thanks for your answer. I think that according to the devs on cryptography's github, this code uses AES-256:

```python
import os

from cryptography.hazmat.primitives.ciphers.aead import AESGCM

to_encrypt = b'secret message'
k = AESGCM.generate_key(256)
iv = os.urandom(32)
a = AESGCM(k)

encrypted = iv + a.encrypt(iv, to_encrypt, None)
print(f'{k = }\n{encrypted = }')

assert to_encrypt == a.decrypt(encrypted[:32], encrypted[32:], None)```

Is this code okay?