code: @Override
      public CreateDefaultSubnetResult createDefaultSubnet(CreateDefaultSubnetRequest request) {
          request = beforeClientExecution(request);
          return executeCreateDefaultSubnet(request);
      }
docs: <p>
  Creates a default subnet with a size <code>/20</code> IPv4 CIDR block in the specified Availability Zone in your
  default VPC. You can have only one default subnet per Availability Zone. For more information, see <a
  href="https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/default-vpc.html#create-default-subnet">Creating a
  Default Subnet</a> in the <i>Amazon Virtual Private Cloud User Guide</i>.
  </p>
  
  @param createDefaultSubnetRequest
  @return Result of the CreateDefaultSubnet operation returned by the service.
  @sample AmazonEC2.CreateDefaultSubnet
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/ec2-2016-11-15/CreateDefaultSubnet" target="_top">AWS API
  Documentation</a>