old_contents: 
  class HopDB(object):
  
      def __init__(self):
          super(HopDB, self).__init__()
          self.hops = {}  # prefix -> hop
          self.installed_prefix = []
  
      def add_hop(self, prefix, next_hop):
          self.hops.setdefault(prefix, next_hop)
  
      def get_nexthop(self, prefix):
          self.hops.get(prefix)
  
      def is_prefix_installed(self, prefix):
          return (prefix in self.installed_prefix)
  
      def get_uninstalled_prefix_list(self):
          result = [prefix for prefix in
                    self.hops.keys() if (prefix not in self.installed_prefix)]
          return result
  
      def install_prefix(self, prefix):
          self.installed_prefix.append(prefix)
  
new_contents: 
  class HopDB(object):
  
      def __init__(self):
          super(HopDB, self).__init__()
          self.hops = {}  # prefix -> hop
          self.installed_prefix = []
  
      def add_hop(self, prefix, next_hop):
          self.hops.setdefault(prefix, next_hop)
  
      def get_nexthop(self, prefix):
          self.hops.get(prefix)
  
      def is_prefix_installed(self, prefix):
          return (prefix in self.installed_prefix)
  
      def get_uninstalled_prefix_list(self):
          result = [prefix for prefix in
                    self.hops.keys() if (prefix not in self.installed_prefix)]
          return result
  
      def install_prefix(self, prefix):
          self.installed_prefix.append(prefix)
  
      def get_all_prefixes(self):
          return hops.keys()
  
subject: Add `get_all_prefixes` to hop_db