code: public synchronized MustacheEngine build() {
          MustacheEngine engine = new DefaultMustacheEngine(this);
          for (EngineBuiltCallback callback : engineReadyCallbacks) {
              callback.engineBuilt(engine);
          }
          BuildInfo buildInfo = BuildInfo.load();
          LOGGER.info("Engine built {} ({})", buildInfo.getVersion(), buildInfo.getTimestampDate());
          LOGGER.debug("Engine configuration: {}",
                  engine.getConfiguration().getInfo());
          isBuilt = true;
          return engine;
      }
docs: Builds the engine instance.
  
  @return the built engine