public static Span currentSpan(Object spanProvider)
    {
        SpanProvider sp = asFacet(SpanProvider.class, spanProvider);
        Span span = (sp == null ? null : sp.currentSpan());
        return span;
    }
public static Span currentSpan ( Object spanProvider ) { SpanProvider sp = asFacet ( SpanProvider . class , spanProvider ) ; Span span = ( sp == null ? null : sp . currentSpan ( ) ) ; return span ; }
Attempts to get a {@link Span} from the given object, if it
supports {@link SpanProvider#currentSpan()}.

@param spanProvider may be null.
@return null if there's not a current span.