code: def cancel(self, contacts):
          
          self.is_in_effect = False
          contact = contacts[self.ref]
          contact.raise_cancel_downtime_log_entry()
          self.can_be_deleted = True
docs: Wrapper to call raise_cancel_downtime_log_entry for ref (host/service)
          set can_be_deleted to True
          set is_in_effect to False
  
          :return: None