Put the needed import in one example

Author: pquentin

docs/api-guide/versioning.md

@@ -31,6 +31,8 @@ How you vary the API behavior is up to you, but one example you might typically
 
 The `reverse` function included by REST framework ties in with the versioning scheme. You need to make sure to include the current `request` as a keyword argument, like so.
 
+    from rest_framework.reverse import reverse
+
     reverse('bookings-list', request=request)
 
 The above function will apply any URL transformations appropriate to the request version. For example: