fixup

Author: HeahDude

reference/constraints/Traverse.rst

@@ -18,7 +18,7 @@ Basic Usage
 
 In the following example, create three classes ``Book``, ``Author`` and ``Editor``
 that all have constraints on their properties. Furthermore, ``Book``
-stores an ``Author`` and an ``Editor`` instances that must be valid too::
+stores an ``Author`` and an ``Editor`` instance that must be valid too::
 
 .. configuration-block::
 
@@ -79,6 +79,7 @@ stores an ``Author`` and an ``Editor`` instances that must be valid too::
         namespace AppBundle\Entity;
 
         use Symfony\Component\Validator\Constraints as Assert;
+        use Symfony\Component\Validator\Mapping\ClassMetadata;
 
         class Book
         {