At first, I elaborated the keyword part of CHECK-LAMBDA after the model
of LAMBDA/KW of Mzlib. (This made my subconsciousness to reference the
reference without reference.)
But now, I think the keyword need not to be limited to a single data
type, and keyword options (such as ALLOW-DUPLICATE-KEYS, ALLOW-BODY,
ALLOW-OTHER-KEYS, ALLOW-ANYTHING, ...) are excrescences. So, I've
submitted a new revised draft.