          ...
  
      def extract_max_priority_page(self):
          """Return the highest priority link in `links_to_crawl`."""
          ...
  
      def insert_crawled_link(self, url, signature):
          """Add the given link to `crawled_links`."""
          ...
  
 
</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 </s> remove         ...
 </s> add         pass
        pass
          ...
  
      def extract_max_priority_page(self):
          """Return the highest priority link in `links_to_crawl`."""
        pass
  
      def insert_crawled_link(self, url, signature):
          """Add the given link to `crawled_links`."""
          ...
  
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