public static boolean maybeSetPong(TraceContext context) {
            if (context.extra().size() == 1) {
                final Object extra = context.extra().get(0);
                if (extra instanceof PingPongExtra) {
                    ((PingPongExtra) extra).pong = true;
                    return true;
                }
            }
            return false;
        }
If the input includes only this extra, set {@link #isPong() pong = true}.
brave/brave6/src/main/java/com/linecorp/armeria/internal/common/brave/TraceContextUtil.java