def derive_fernet_key(input_key):
hkdf = HKDF(<EOL>algorithm=hashes.SHA256(),<EOL>length=<NUM_LIT:32>,<EOL>salt=salt,<EOL>info=info,<EOL>backend=backend,<EOL>)<EOL>return base64.urlsafe_b64encode(hkdf.derive(force_bytes(input_key)))<EOL>
Derive a 32-bit b64-encoded Fernet key from arbitrary input key.