docs: def delete(self, subnet_id):
          """
          This is bad delete function
          because one vpc can have more than one subnet.
          It is Ok if user only use CAL for manage cloud resource
          We will update ASAP.
          """
          # 1 : show subnet
          subnet = self.client.describe_subnets(
              SubnetIds=[subnet_id]).get('Subnets')[0]
          vpc_id = subnet.get('VpcId')
          # 2 : delete subnet
          self.client.delete_subnet(SubnetId=subnet_id)
          # 3 : delete vpc
          return self.client.delete_vpc(VpcId=vpc_id)