title: How can i get the output of this map in my data collection
body: <p>i want to the image url from this collection.....
  but i keep getting error like</p>
  <pre><code>Class 'QuerySnapshot' has no instance method 'call'.
  Receiver: Instance of 'QuerySnapshot'
  Tried calling: call()
  </code></pre>
  <p>here is my code</p>
  <pre><code>StaggeredGridView.countBuilder(
              crossAxisCount: 4,
              itemCount: snapshot.data.docs.length,
              itemBuilder: (BuildContext context, int index) =&gt; Container(
                color: Colors.green,
                child: Card(
                  semanticContainer: true,
                  clipBehavior: Clip.antiAliasWithSaveLayer,
                  child: Image.network(
                    snapshot.data.docs[index]
                        .data()['favourite'][0]
                        .profilePictureUrl,
                    fit: BoxFit.fill,
                  ),
                  shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(20.0),
                  ),
                  elevation: 5,
                  margin: EdgeInsets.all(10),
                ),
              ),
  </code></pre>
  <p><a href="https://i.stack.imgur.com/9xMMu.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9xMMu.png" alt="enter image description here" /></a></p>
  <p>Thanks in advance.....
  Thanks</p>