Fixed a spelling mistake

guides/v2.1/extension-dev-guide/extension_attributes/adding-attributes.md

@@ -98,7 +98,7 @@ public function afterSave
 }
 {% endhighlight %}
 
-But if some entity doesn't have implementation to fetch extension attributes, we will always retrieve `null` and each time when we fetch extension atrributes we need to check if they are `null` - need to create them. To avoid such code duplication, we need to create `afterGet` plugin for our entity with extension attributes.
+But if some entity doesn't have implementation to fetch extension attributes, we will always retrieve `null` and each time when we fetch extension attributes we need to check if they are `null` - need to create them. To avoid such code duplication, we need to create `afterGet` plugin for our entity with extension attributes.
 
 Let's assume the product entity doesn't have any implementation of extension attributes, so our plugin might looks like this: