          self.signature = self.create_signature()
  
      def create_signature(self):
          # Create signature based on url and contents
          ...
  
  
  class Crawler(object):
  
      def __init__(self, pages, data_store, reverse_index_queue, doc_index_queue):
 
</s> remove     def move_to_front(self, node):  # ...
    def append_to_front(self, node):  # ...
    def remove_from_tail(self):  # ...
 </s> add     def move_to_front(self, node):
        pass

    def append_to_front(self, node):
        pass

    def remove_from_tail(self):
        pass </s> remove     def message_user(self, friend_id, message):  # ...
    def message_group(self, group_id, message):  # ...
    def send_friend_request(self, friend_id):  # ...
    def receive_friend_request(self, friend_id):  # ...
    def approve_friend_request(self, friend_id):  # ...
    def reject_friend_request(self, friend_id):  # ...
 </s> add     def message_user(self, friend_id, message):
        pass

    def message_group(self, group_id, message):
        pass

    def send_friend_request(self, friend_id):
        pass

    def receive_friend_request(self, friend_id):
        pass

    def approve_friend_request(self, friend_id):
        pass

    def reject_friend_request(self, friend_id):
        pass </s> remove     def add_user(self, user_id, name, pass_hash):  # ...
    def remove_user(self, user_id):  # ...
    def add_friend_request(self, from_user_id, to_user_id):  # ...
    def approve_friend_request(self, from_user_id, to_user_id):  # ...
    def reject_friend_request(self, from_user_id, to_user_id):  # ...
 </s> add     def add_user(self, user_id, name, pass_hash):
        pass

    def remove_user(self, user_id):
        pass

    def add_friend_request(self, from_user_id, to_user_id):
        pass

    def approve_friend_request(self, from_user_id, to_user_id):
        pass

    def reject_friend_request(self, from_user_id, to_user_id):
        pass </s> remove     def __init__(self, db);
 </s> add     def __init__(self, db): </s> remove     def add_user(self, user):  # ...
    def remove_user(self, user):  # ... 
 </s> add     def add_user(self, user):
        pass

    def remove_user(self, user):
        pass
        pass
          self.signature = self.create_signature()
  
      def create_signature(self):
          # Create signature based on url and contents
        pass
  
  
  class Crawler(object):
  
      def __init__(self, pages, data_store, reverse_index_queue, doc_index_queue):
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