old_contents: from abc import ABCMeta
  from abc import abstractmethod
  
  
  class NetworkingHandlerInterface:
      __metaclass__ = ABCMeta
  
      @abstractmethod
      def send_command(self, cmd, expected_str=None, timeout=30):
          pass
  
      @abstractmethod
      def restore_configuration(self, source_file, clear_config='override'):
          pass
  
      @abstractmethod
      def backup_configuration(self, destination_host, source_filename):
          pass
  
      @abstractmethod
      def normalize_output(self, output):
          pass
  
      @abstractmethod
      def update_firmware(self, remote_host, file_path):
          pass
  
      @abstractmethod
      def discover_snmp(self):
          pass
  
new_contents: from abc import ABCMeta
  from abc import abstractmethod
  
  
  class NetworkingHandlerInterface:
      __metaclass__ = ABCMeta
  
      @abstractmethod
      def add_vlan(self, vlan_range, port_list, port_mode, additional_info):
          pass
  
      @abstractmethod
      def remove_vlan(self, vlan_range, port_list, port_mode, additional_info):
          pass
  
      @abstractmethod
      def send_command(self, cmd, expected_str=None, timeout=30):
          pass
  
      @abstractmethod
      def restore_configuration(self, source_file, clear_config='override'):
          pass
  
      @abstractmethod
      def backup_configuration(self, destination_host, source_filename):
          pass
  
      @abstractmethod
      def normalize_output(self, output):
          pass
  
      @abstractmethod
      def update_firmware(self, remote_host, file_path):
          pass
  
      @abstractmethod
      def discover_snmp(self):
          pass
  
subject: add add_remove vlan