code: public static void setOptId(String customOptId) {
          TracyThreadContext ctx = threadContext.get();
          if (isValidContext(ctx))    {
              ctx.setOptId(customOptId);
          }
      }
docs: Allows user to set a custom optId (usually automatically created)
  This method can be safely called any time between a 'before' and 'after'
  
  @param customOptId is the String which will be recorded as Tracy optId. Best practice is to use a 4 character string outside of 32bit hex pattern [0000..1111]
  e.g. setOptId("U001")