code: function isExportsStatement(expression) {
  
      var type, object, property;
  
      type = expression.type;
      object = expression.object;
      property = expression.property;
  
      return type === 'MemberExpression' && object && object.name === 'exports' && property && property.type === 'Identifier';
  
  }
docs: 返回expression是否为exports语句