title: 'DocumentSnapshot' is not a subpyte of type of 'String'
body: <p>I want to access images from url saved in FireStore, but I get error from the title</p>
  <pre><code>  @override
    Widget build(BuildContext context) {
      return MaterialApp(
          theme: ThemeData(brightness: Brightness.dark),
          home: StreamBuilder(
              stream: Firestore.instance.collection('images').snapshots(),
              builder: (context, snapshot) {
                if (!snapshot.hasData) return CircularProgressIndicator();
                for (int i = 0; i &lt; snapshot.data.documents.length; i++) {
                  return ListWheelScrollView(children: &lt;Widget&gt;[
                    Image.network(snapshot.data.documents[i]),
                  ]);
                }
              }));
    }
  }
  </code></pre>
  <p><img src="https://i.stack.imgur.com/MRopJ.png" alt="my firebase collection" /></p>