code: @Override
      public XValue call(Scope scope) {
          NodeTest textFun = Scanner.findNodeTestByName("allText");
          XValue textVal = textFun.call(scope);
          String whole = StringUtils.join(textVal.asList(),"");
          Matcher matcher = numExt.matcher(whole);
          if (matcher.find()){
              String numStr = matcher.group();
              BigDecimal num = new BigDecimal(numStr);
              return XValue.create(num.doubleValue());
          }else {
              return XValue.create(null);
          }
      }
docs: 函数具体逻辑
  
  @param scope 上下文
  @return 计算好的节点