private Optional<TensorType> transformerTokensFeatureType(Reference reference) {
        if ( ! reference.name().equals("tokenTypeIds") &&
                ! reference.name().equals("tokenInputIds") &&
                ! reference.name().equals("tokenAttentionMask"))
            return Optional.empty();

        if ( ! (reference.arguments().size() > 1))
            throw new IllegalArgumentException(reference.name() + " must have at least 2 arguments");

        ExpressionNode size = reference.arguments().expressions().get(0);
        return Optional.of(TokenTransformer.createTensorType(reference.name(), size));
    }
Returns the binding if this reference is a simple identifier which is bound in this context.
Returns empty otherwise.
config-model/src/main/java/com/yahoo/schema/MapEvaluationTypeContext.java