Creates a new subnet group.Show details from next link. https://docs.aws.amazon.com/ja_jp/cli/latest/reference/dax/create-subnet-group.html
| aws dax create-subnet-group \ |
| Step 1: Create a Subnet Group - Amazon DynamoDB : http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DAX.create-cluster.cli.create-subnet-group.html |