title: GraphQL Node.js: determine what types are used within a query
body: <p>Given I have a schema that has types: User, Comment, Post, Image; Is it possible to determine the GraphQL types being used in a query, given the query and schema?
  e.g. if a client had a query </p>
  
  <pre><code>{
      user(userName: "username") {
          email
          comments
      }
  }
  </code></pre>
  
  <p>In this case, the query has types User and Comment. Is it possible to determine the programmatically using either the graphql-js or graphql packages for node.js? </p>