The key isn’t in the document. And you need to specify it to get the document, so you already have it.
Also - the example has the result indexed with (0), because it only retries 1 property. So if you’re indexing the result with (0), you’ll only see the first property as well.
from datetime import timedelta
import couchbase.subdocument as SD
from couchbase.options import LookupInOptions
# ... other code ...
key = 'hotel_10025'
res = collection.lookup_in(key,
(SD.get("geo"),),
LookupInOptions(timeout=timedelta(seconds=2)))
print(f'Hotel {key} coordinates: {res.content_as[dict](0)}')