code: def within_ipv4_network(self, field, values):
          
          v = ['ipv4_net("%s")' % net for net in values]
          self.update_filter('{} IN union({})'.format(field, ','.join(v)))
docs: This filter adds specified networks to a filter to check
          for inclusion.
          
          :param str field: name of field to filter on. Taken from 'Show Filter
              Expression' within SMC.
          :param list values: network definitions, in cidr format, i.e: 1.1.1.0/24.