          ...
  
      def insert_crawled_link(self, url, signature):
          """Add the given link to `crawled_links`."""
          ...
  
      def crawled_similar(self, signature):
          """Determine if we've already crawled a page matching the given signature"""
          ...
  
 
</s> remove         ...
 </s> add         pass </s> remove         ...
 </s> add         pass </s> remove         ...
 </s> add         pass </s> remove         ...
 </s> add         pass </s> remove         ...
 </s> add         pass
        pass
          ...
  
      def insert_crawled_link(self, url, signature):
          """Add the given link to `crawled_links`."""
        pass
  
      def crawled_similar(self, signature):
          """Determine if we've already crawled a page matching the given signature"""
          ...
  
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