parsing nested api responses — without crashing on a missing key

AI wrote a parser that uses chained .get without defaults. When a field is missing, the chain returns None and the function quietly returns None. The caller has no idea anything went wrong, so the bug surfaces somewhere unrelated.

Fix the function to raise ValueError(f"missing field: {field}") whenever the field can't be found. Specifically:

• If choices is missing or the list is empty, raise with field "choices".
• If message is missing on the first choice, raise with field "message".
• If content is missing, raise with field "content".

The starter has a response missing content. Wrap the call in try/except ValueError as err: print(err).

Expected output:

missing field: content