text: """ abstract vpp object and object registry """
  
  import abc
  import six
  
  from six import moves
  
  
  @six.add_metaclass(abc.ABCMeta)
  class VppObject(object):
      """ Abstract vpp object """
  
      @abc.abstractmethod
      def add_vpp_config(self):
          """ Add the configuration for this object to vpp. """
          pass
  
      @abc.abstractmethod
      def query_vpp_config(self):
          """Query the vpp configuration.
  
          :return: True if the object is configured"""
          pass
  
      @abc.abstractmethod
      def remove_vpp_config(self):
          """ Remove the configuration for this object from vpp. """
          pass
  
      def object_id(self):
          """ Return a unique string representing this object. """
          return "Undefined. for <%s %s>" % (self.__class__.__name__, id(self))
  
      def __str__(self):
          return self.object_id()
  
      def __repr__(self):
          return '<%s>' % self.object_id()
  
      def __hash__(self):
          return hash(self.object_id())
  
      def __eq__(self, other):
          if not isinstance(other, self.__class__):
              return NotImplemented
          if other.object_id() == self.object_id():
              return True
          return False
  
      # This can be removed when python2 support is dropped.
      def __ne__(self, other):
          return not self.__eq__(other)
  
  
  class VppObjectRegistry(object):
      """ Class which handles automatic configuration cleanup. """
      _shared_state = {}
  
      def __init__(self):
          self.__dict__ = self._shared_state
          if not hasattr(self, "_object_registry"):
              self._object_registry = []
          if not hasattr(self, "_object_dict"):
              self._object_dict = dict()
  
      def register(self, obj, logger):
          """ Register an object in the registry. """
          if obj.object_id() not in self._object_dict:
              self._object_registry.append(obj)
              self._object_dict[obj.object_id()] = obj
              logger.debug("REG: registering %s" % obj)
          else:
              logger.debug("REG: duplicate add, ignoring (%s)" % obj)
  
      def unregister_all(self, logger):
          """ Remove all object registrations from registry. """
          logger.debug("REG: removing all object registrations")
          self._object_registry = []
          self._object_dict = dict()
  
      def remove_vpp_config(self, logger):
          """
          Remove configuration (if present) from vpp and then remove all objects
          from the registry.
          """
          if not self._object_registry:
              logger.info("REG: No objects registered for auto-cleanup.")
              return
          logger.info("REG: Removing VPP configuration for registered objects")
          # remove the config in reverse order as there might be dependencies
          failed = []
          for obj in reversed(self._object_registry):
              if obj.query_vpp_config():
                  logger.info("REG: Removing configuration for %s" % obj)
                  obj.remove_vpp_config()
                  if obj.query_vpp_config():
                      failed.append(obj)
              else:
                  logger.info(
                      "REG: Skipping removal for %s, configuration not present" %
                      obj)
          self.unregister_all(logger)
          if failed:
              logger.error("REG: Couldn't remove configuration for object(s):")
              for obj in failed:
                  logger.error(repr(obj))
              raise Exception("Couldn't remove configuration for object(s): %s" %
                              (", ".join(str(x) for x in failed)))
  