Fix bug in validators documentation (#8779)

FlorisHoogenboom · web-flow · commit 614bd87b601c · 2022-12-01T22:13:14.000+06:00
Function validators seem to have to return their value (which will become part of `validated_data`) as part of their signature.
diff --git a/docs/api-guide/validators.md b/docs/api-guide/validators.md
@@ -271,6 +271,7 @@ A validator may be any callable that raises a `serializers.ValidationError` on f
     def even_number(value):
         if value % 2 != 0:
             raise serializers.ValidationError('This field must be an even number.')
+        return value
 
 #### Field-level validation
 
