code: def linkify_sd_by_s(self, hosts, services):
          to_del = []
          errors = self.configuration_errors
          warns = self.configuration_warnings
          for servicedep in self:
              try:
                  s_name = servicedep.dependent_service_description
                  hst_name = servicedep.dependent_host_name
                  serv = services.find_srv_by_name_and_hostname(hst_name, s_name)
                  if serv is None:
                      host = hosts.find_by_name(hst_name)
                      if not (host and host.is_excluded_for_sdesc(s_name)):
                          errors.append("Service %s not found for host %s" % (s_name, hst_name))
                      elif host:
                          warns.append("Service %s is excluded from host %s ; "
                                       "removing this servicedependency as it's unusuable."
                                       % (s_name, hst_name))
                      to_del.append(servicedep)
                      continue
                  servicedep.dependent_service_description = serv.uuid
                  s_name = servicedep.service_description
                  hst_name = servicedep.host_name
                  serv = services.find_srv_by_name_and_hostname(hst_name, s_name)
                  if serv is None:
                      host = hosts.find_by_name(hst_name)
                      if not (host and host.is_excluded_for_sdesc(s_name)):
                          errors.append("Service %s not found for host %s" % (s_name, hst_name))
                      elif host:
                          warns.append("Service %s is excluded from host %s ; "
                                       "removing this servicedependency as it's unusuable."
                                       % (s_name, hst_name))
                      to_del.append(servicedep)
                      continue
                  servicedep.service_description = serv.uuid
              except AttributeError as err:
                  logger.error("[servicedependency] fail to linkify by service %s: %s",
                               servicedep, err)
                  to_del.append(servicedep)
          for servicedep in to_del:
              self.remove_item(servicedep)