RepresentationModelProcessor processes CollectionModel of alien entities

In my Spring Boot project, I have two entities like Seller and Buyer. By extending CrudRepository, I enable Spring Data REST to automatically create a CollectionModel for each of them accessible via corresponding endpoints like /sellers and /buyers. Now, I want to add a custom "filter"-link to the CollectionModel for Buyer by writing a RepresentationModelProcessor like this:

@Component
public class BuyerCollectionModelProcessor implements
        RepresentationModelProcessor<CollectionModel<Buyer>> {

    @Override
    public CollectionModel<Buyer> process(CollectionModel<Buyer> model) {
	// here we add a link to some filter() method from BuyersController class
        return model.add(linkTo(methodOn(BuyersController.class)
				.filterBy(Optional.empty(), Optional.empty()))
					.withRel("filter"));
    }
}

It works as expected with the /buyers endpoint which now includes "filter"-link:

  "_links": {
        "self": {
            "href": "http://localhost:8080/buyers"
        },
        "filter": {
            "href": "http://localhost:8080/buyers/filterBy{?city,age}",
            "templated": true
        }
    }

But as a side-effect, the /sellers endpoint now also gets the buyers "filter"-link:

  "_links": {
        "self": {
            "href": "http://localhost:8080/sellers"
        },
        "filter": {
            "href": "http://localhost:8080/buyers/filterBy{?city,age}",
            "templated": true
        }
    }

And if I decide to add a custom link to /sellers in a similar way, then /sellers and /buyers will have the two links each. How can I fix that and separate custom links, so that they are included only in the CollectionModel for their corresponding entities?