title: How to specify alternative response formats with swagger/OpenAPI?
body: <p>I have a <a href="http://swagger.io/" rel="noreferrer"><code>swagger.yaml</code></a> something like this:</p>
  
  <pre><code>swagger: "2.0"
  paths:
    /something:
      get:
        parameters:
          - name: format
            in: query
            type: string
            pattern: '^(csv|json|xml)$'
        responses:
          200:
            schema:
              type: ?
  </code></pre>
  
  <p>And I want to return different formats (csv, json, xml) depending on the value of the <code>format</code> query parameter (eg. localhost/api/something?format=csv).</p>
  
  <p>How can I specify the different response formats in the spec?</p>