code: protected void __internalBuild() {
          w_ = null; // reset output destination
          try {
              long l = 0l;
              if (__logTime()) {
                  l = System.currentTimeMillis();
              }
              final String code = secureCode;
              Sandbox.enterRestrictedZone(code);
              try {
                  __internalInit();
                  build();
              } finally {
                  __finally();
                  Sandbox.leaveCurZone(code);
              }
              if (__logTime()) {
                  __logger.debug("<<<<<<<<<<<< [%s] build: %sms", getClass().getName(), System.currentTimeMillis() - l);
              }
          } catch (RythmException e) {
              throw e;
          } catch (Throwable e) {
              handleThrowable(e);
          }
          if (null != w_) {
              try {
                  IO.writeContent(toString(), w_);
                  w_ = null;
              } catch (Exception e) {
                  Logger.error(e, "failed to write template content to output destination");
              }
          }
      }
docs: Not to be used in user application or template