private boolean areUnknownTraitsAllowed() {
        Object allowUnknown = properties.get(ModelAssembler.ALLOW_UNKNOWN_TRAITS);
        return allowUnknown != null && (boolean) allowUnknown;
    }
Assembles the model and returns the validated result.

@return Returns the validated result that optionally contains a Model
 and validation events.
smithy-model/src/main/java/software/amazon/smithy/model/loader/ModelAssembler.java