code: def linkify(self, timeperiods, contacts, services, hosts):
          
          self.linkify_with_timeperiods(timeperiods, 'escalation_period')
          self.linkify_with_contacts(contacts)
          self.linkify_es_by_s(services)
          self.linkify_es_by_h(hosts)
docs: Create link between objects::
  
           * escalation -> host
           * escalation -> service
           * escalation -> timeperiods
           * escalation -> contact
  
          :param timeperiods: timeperiods to link
          :type timeperiods: alignak.objects.timeperiod.Timeperiods
          :param contacts: contacts to link
          :type contacts: alignak.objects.contact.Contacts
          :param services: services to link
          :type services: alignak.objects.service.Services
          :param hosts: hosts to link
          :type hosts: alignak.objects.host.Hosts
          :return: None