title: Flutter Firebase get documents by array of IDs
body: <p>How would I get a Query of documents from a collection using a list of IDs? Let's says I have the following:</p>
  
  <pre><code>List&lt;String&gt; someList = ['abc123', 'def456', 'hij789']; // Need to query for these documentIDs
  </code></pre>
  
  <p>I would normally do the following. But this obviously won't work since I need to query the documentIDs.</p>
  
  <pre><code>Query query = Firestore.instance
          .collection(APIPath.products())
          .where('someField', whereIn: someList);
  </code></pre>