class Trace {

    public Span startSpan(String operationName, SpanContext spnContext){
        Span span;
        if (spnContext!= null){
            span = modelServiceApiTracer.buildSpan(operationName).asChildOf(spnContext).start();
        }
        else {
            span = modelServiceApiTracer.buildSpan(operationName).start();
        }
        return span;
    }

    @Autowired public  Trace(Tracer tracer);

}