Source

File: wp-includes/rest-api/endpoints/class-wp-rest-controller.php

public function prepare_response_for_collection( $response ) {
		if ( ! ( $response instanceof WP_REST_Response ) ) {
			return $response;
		}

		$data   = (array) $response->get_data();
		$server = rest_get_server();
		$links  = $server::get_compact_response_links( $response );

		if ( ! empty( $links ) ) {
			$data['_links'] = $links;
		}

		return $data;
	}