This filter is used to register CRUD instance. As long as the instance is not registered it won't be effective. Typically, Crud instance is called using their identifier. That's why we need to replace it, using this filter, with a relevant Crud class.

Here is how you'll catch crud identifiers :

In the above example, we're trying to replace "ns.my-crud-identifier" which is the identifier of our Crud class (in our example), with the related class `MyOrdersCrud`. It's important to return the identifier as it's provided if it doesn't match any of the identifiers you have defined on your Crud classes.