docs: function execImport(importation, froms) {
      if (!importation) {
        return importation;
      }
      if (importation.indexOf('#') === 0) { // variants
        if (froms instanceof Array && froms.indexOf('variant') < 0) {
          return importation;
        }
        return getVariant(importation.slice(1));
      }
      if (importation.indexOf('@') === 0) { // argv
        if (froms instanceof Array && froms.indexOf('argv') < 0) {
          return importation;
        }
        return getArgument(importation.slice(1));
      }
      if (importation.indexOf(':') === 0) { // env
        if (froms instanceof Array && froms.indexOf('env') < 0) {
          return importation;
        }
        return getEnvironment(importation.slice(1));
      }
      if (/^'([^\\']*(\\.)*)*'$/.test(importation)) { // 字符串输出
        /*jslint evil: true */
        return new Function('return (' + importation + ');')();
      }
      if (/^[\[\{"]/.test(importation)) { // 可能是 JSON
        return importation;
      }
      if (froms instanceof Array && froms.indexOf('file') < 0) {
        return importation;
      }
      // file
      var items = importation.split('?');
      var name = items[0];
      if (invalidFilename(name)) { // 无效文件名
        return importation;
      }
      var selector = items[1];
      var scope;
      if (!name) {
        scope = instance;
      }
      else {
        var file = path.resolve(getDirname(), name);
        if (!fs.existsSync(file)) { // 文件不存在原样
          return importation;
        }
        if (execExclude(file)) {
          if (!selector) {
            return String(fs.readFileSync(file));
          }
          else {
            console.error(
              colors.red('File "%s" has been ruled exclude, unable to code block import.'), file
            );
            return '';
          }
        }
        scope = fileScope(file);
      }
      if (selector) {
        var node = scope.querySelector(selector);
        if (!node) {
          console.error(
            colors.red('Selector "%s" is no matching nodes.'), selector
          );
          return '';
        }
        if (node instanceof Array) {
          return node.map(function (item) {
            return scope.buildBlock(item, true);
          }).join('\n');
        }
        return scope.buildBlock(node, true);
      }
      else {
        if (instance === scope) { // 不能引用自己
          console.error(
            colors.red('Cannot reference himself.')
          );
          return '';
        }
        return scope.build(instance);
      }
    }