Return a fully-qualified product_set string.

def product_set_path(cls, project, location, product_set):
        """Return a fully-qualified product_set string."""
        return google.api_core.path_template.expand(
            "projects/{project}/locations/{location}/productSets/{product_set}",
            project=project,
            location=location,
            product_set=product_set,
        )