def del_contact_downtime(self, downtime_id):
        """Delete a contact downtime
        Format of the line that triggers function call::

        DEL_CONTACT_DOWNTIME;<downtime_id>

        :param downtime_id: downtime id to delete
        :type downtime_id: int
        :return: None
        """
        for item in self.daemon.contacts:
            if downtime_id in item.downtimes:
                item.downtimes[downtime_id].cancel(self.daemon.contacts)
                break
        else:
            self.send_an_element(make_monitoring_log(
                'warning', 'DEL_CONTACT_DOWNTIME: downtime id: %s does not exist '
                           'and cannot be deleted.' % downtime_id))