code: private CreateSubnetResponseType createSubnet(final String vpcId, final String cidrBlock) {
          CreateSubnetResponseType ret = new CreateSubnetResponseType();
          ret.setRequestId(UUID.randomUUID().toString());
          MockSubnet mockSubnet = mockSubnetController.createSubnet(cidrBlock, vpcId);
  
          SubnetType subnetType = new SubnetType();
          subnetType.setVpcId(mockSubnet.getVpcId());
          subnetType.setSubnetId(mockSubnet.getSubnetId());
  
          ret.setSubnet(subnetType);
          return ret;
      }
docs: Handles "createSubnet" request to create Subnet and returns response with a subnet.
  @param vpcId vpc Id for subnet.
  @param cidrBlock VPC cidr block.
  @return a CreateSubnetResponseType with our new Subnet