title: Equivalent use of oneOf (from OpenAPI 3) in OpenAPI 2
body: <p>How can I adjust this snippet with <code>oneOf</code> to the equivalent OpenAPI 2.0 version?</p>
  <pre class="lang-yaml prettyprint-override"><code>  formats:
      type: array
      description: Possible parameter format.
      items:
        oneOf:
        - type: string
        - type: object
          description: Matched alias formats
          properties:
            representation:
              type: array
              description: Alias format representations
              items:
                type: string
            match_multiple:
              type: boolean
              optional: true
            display:
              type: string
              description: Display string of alias format
  </code></pre>