How to iterate over the contraints returned by get_attrs/2?

I’m playing around with constraints but am stuck on how to iterate through the attributes assigned to a variable. The second argument of get_attrs/2 won’t unify with a term of the form att(A, B, C):

:- module(noun, [noun/2]).

noun(TypeName, X) :-
    put_attr(X, noun, TypeName).

resolveConstraints(Variable, Value) :-
    % Docs say that second argument returns something in the form: 
    % att(module, value, More)
    get_attrs(Variable, Attrs),
    % This fails...
    Attrs = att(Module, Value, []).

?- noun("rock", X), resolveConstraints(X, a).

What am I missing?

I think it fails because argument Value=a while att Value=rock, i.e., simple unification failure.

Oh geez :man_facepalming:. I suspected it was something dumb. I meant to name the head variable something else…Thanks…