code: def add_service_listener(
          self, bundle_context, listener, specification=None, ldap_filter=None
      ):
          
          if listener is None or not hasattr(listener, "service_changed"):
              raise BundleException("Invalid service listener given")
  
          with self.__svc_lock:
              if listener in self.__listeners_data:
                  self._logger.warning(
                      "Already known service listener '%s'", listener
                  )
                  return False
  
              try:
                  ldap_filter = ldapfilter.get_ldap_filter(ldap_filter)
              except ValueError as ex:
                  raise BundleException("Invalid service filter: {0}".format(ex))
  
              stored = ListenerInfo(
                  bundle_context, listener, specification, ldap_filter
              )
              self.__listeners_data[listener] = stored
              self.__svc_listeners.setdefault(specification, []).append(stored)
              return True
docs: Registers a service listener
  
          :param bundle_context: The bundle_context of the service listener
          :param listener: The service listener
          :param specification: The specification that must provide the service
                                (optional, None to accept all services)
          :param ldap_filter: Filter that must match the service properties
                              (optional, None to accept all services)
          :return: True if the listener has been registered, False if it was
                   already known
          :raise BundleException: An invalid listener has been given