block sequence:
··- one↓
  - two : three↓

port: &ports
  adapter:  postgres
  host:     localhost

development:
  database: myapp_development
  <<: *ports

{
   "port": {
      "adapter": "postgres",
      "host": "localhost"
   },
   "development": {
      "database": "myapp_development",
      "adapter": "postgres",
      "host": "localhost"
   }
}