code: def get_all_subnets_cidr(self, no_mask=False):
          
          body = {}
          subnet_cidrs = []
          try:
              subnet_list = self.neutronclient.list_subnets(body=body)
              subnet_dat = subnet_list.get('subnets')
              for sub in subnet_dat:
                  if no_mask:
                      subnet_cidrs.append(sub.get('cidr').split('/')[0])
                  else:
                      subnet_cidrs.append(sub.get('cidr'))
          except Exception as exc:
              LOG.error("Failed to list subnet Exc %s", str(exc))
          return subnet_cidrs
docs: Returns all the subnets.