docs: public Expression generateMsgGroupVariable(MsgFallbackGroupNode node) {
      String tmpVarName = translationContext.nameGenerator().generateName("msg_s");
      Expression msg;
      if (node.numChildren() == 1) {
        translationContext
            .soyToJsVariableMappings()
            .setIsPrimaryMsgInUse(node, Expression.LITERAL_TRUE);
        msg = generateSingleMsgVariable(node.getChild(0), tmpVarName);
      } else { // has fallbackmsg children
        msg = generateMsgGroupVariable(node, tmpVarName);
      }
      // handle escaping
      for (SoyPrintDirective printDirective : node.getEscapingDirectives()) {
        msg =
            SoyJsPluginUtils.applyDirective(
                msg,
                (SoyJsSrcPrintDirective) printDirective,
                /* args= */ ImmutableList.of(),
                node.getSourceLocation(),
                errorReporter);
      }
      return msg;
    }