  class PagesDataStore(object):
  
      def __init__(self, db);
          self.db = db
          ...
  
      def add_link_to_crawl(self, url):
          """Add the given link to `links_to_crawl`."""
          ...
  
 
</s> remove     def __init__(self, db);
 </s> add     def __init__(self, db): </s> remove         ...
 </s> add         pass </s> remove         ...
 </s> add         pass </s> remove     def reduce_priority_link_to_crawl(self, url)
 </s> add     def reduce_priority_link_to_crawl(self, url): </s> remove         ...
 </s> add         pass
        pass
  class PagesDataStore(object):
  
      def __init__(self, db);
          self.db = db
        pass
  
      def add_link_to_crawl(self, url):
          """Add the given link to `links_to_crawl`."""
          ...
  
keep keep keep keep replace keep keep keep keep keep
 Convert all .py files to be valid Python (#98) 
solutions/system_design/web_crawler/web_crawler_snippets.py