title: GraphQL fragment of fragments
body: <p>I have a GraphQL query like this:</p>
  
  <pre><code>import { gql } from 'apollo-boost';
  
  export default gql`
    {
      pageHomeCollection(limit: 1) {
        items {
          navigationLinkLeft {
            ... on PageBasic {
              slug
              title
            }
            ... on PageShop {
              title
            }
            ... on PostCollection {
              slug
              title
            }
          }
          navigationLinkRight {
            ... on PageBasic {
              slug
              title
            }
            ... on PageShop {
              title
            }
            ... on PostCollection {
              slug
              title
            }
          }
          title
        }
      }
    }
  `;
  </code></pre>
  
  <p>The requested data for both <code>navigationLinkLeft</code> and <code>navigationLinkRight</code> are the same, so I'd like to avoid the duplication. I know about fragments, but not sure if it's possible to extract the 3 <code>... on</code> because I'm not sure what type the fragment would be. Is this possible?</p>