old_contents: class Common:
      def __init__(self):
          pass
      
      def remove_enter(self, url):
          '''
          @usage: remote all /n in url path
          @arg: plug in an url path
          @return: return cleaned url
          '''
          return url.strip()      
  
      def clean_feature(self, feature_list):
          '''
          @usage: clean feature list, remove all spaces
          @arg: list of feature
          @return: furniture feature list
          ''' 
          feature_list = [x.strip(' ').replace("\n","") for x in feature_list]
          feature_list = [' '.join(x.split()) for x in feature_list]
          return feature_list
  
      def clean_reviews(self, review_list):
          '''
          @usage: clean review list, remove all spaces
          @arg: list of reviews
          @return: cleaned review list
          '''
          review_list = [x.strip(' ').replace("\n","") for x in review_list]
          review_list = [' '.join(x.split()) for x in review_list]
          return review_list
  
new_contents: class Common:
      def __init__(self):
          pass
      
      def remove_enter(self, url):
          '''
          @usage: remote all /n in url path
          @arg: plug in an url path
          @return: return cleaned url
          '''
          return url.strip()      
  
      def clean_feature(self, feature_list):
          '''
          @usage: clean feature list, remove all spaces
          @arg: list of feature
          @return: furniture feature list
          ''' 
          feature_list = [x.strip(' ').replace("\n","") for x in feature_list]
          feature_list = [' '.join(x.split()) for x in feature_list]
          return feature_list
  
      def clean_reviews(self, review_list):
          '''
          @usage: clean review list, remove all spaces
          @arg: list of reviews
          @return: cleaned review list
          '''
          review_list = [x.strip(' ').replace("\n","") for x in review_list]
          review_list = [' '.join(x.split()) for x in review_list]
          return review_list
  
      def clean_filename(self, filename):
          '''
          @usage: modify filename, make sure there is no invaild symbol
          @arg: a filename
          @return: filename with no invalid symbol
          '''
          clean_filename = filename.replace(' ','_').translate(None, '/!@#$*\\')
          return clean_filename
  
subject: add clean_filename function