@Override
    public boolean equals(Object o) {
        if ( ! (o instanceof ModelReference other)) return false;
        if ( ! Objects.equals(this.modelId, other.modelId)) return false;
        if ( ! Objects.equals(this.url, other.url)) return false;
        if ( ! Objects.equals(this.path, other.path)) return false;
        if ( ! Objects.equals(this.resolved, other.resolved)) return false;
        return true;
    }
Returns the path to the file containing this model, or null if this is unresolved.
config-lib/src/main/java/com/yahoo/config/ModelReference.java