anchor.diff:  
   To use the Docker plugin, add the `plugins` attribute to your command step. In this example, the `yarn` commands will be run inside a Docker container using the node:7 Docker image:
   
  -```
  +```yml
   steps:
     - command: yarn install && yarn run test
       plugins:
  
positive.code: 
  Another example of a production `docker-compose.yml` configuration is from the [buildkite-agent Golang source code](https://github.com/buildkite/agent):
  
  ```
  version: '2.1'
  services:
    agent:
  
negative.code: 
  At the start of your `pipeline.yml`, add a step to build an image with the Docker plugin. In this example, we use the `docker-compose` plugin to prebuild the `app` image and upload it to a registry:
  
  ```yml
  steps:
    - name: "Docker Build"
      plugins:
  