protected function upgradeChapterTypes() {
		$type_1 = get_term_by( 'slug', 'type-1', 'chapter-type' );
		$type_2 = get_term_by( 'slug', 'type-2', 'chapter-type' );
		$type_3 = get_term_by( 'slug', 'type-3', 'chapter-type' );
		$type_4 = get_term_by( 'slug', 'type-4', 'chapter-type' );
		$type_5 = get_term_by( 'slug', 'type-5', 'chapter-type' );

		if ( $type_1 ) {
			wp_update_term(
				$type_1->term_id, 'chapter-type', [
					'name' => 'Standard',
					'slug' => 'standard',
				]
			);
		}

		if ( $type_2 ) {
			wp_delete_term( $type_2->term_id, 'chapter-type' );
		}

		if ( $type_3 ) {
			wp_delete_term( $type_3->term_id, 'chapter-type' );
		}

		if ( $type_4 ) {
			wp_delete_term( $type_4->term_id, 'chapter-type' );
		}

		if ( $type_5 ) {
			wp_delete_term( $type_5->term_id, 'chapter-type' );
		}
	}