protected function pre_save( $id ) {
		if ( empty( $id ) ) {
			return;
		}

		$data = $this->get_pre_data();

		foreach ( $data as $key => $value ) {
			if ( empty( $value ) ) {
				continue;
			}

			if ( is_array( $value ) ) {
				list( $keys, $value ) = $this->get_pre_deep_keys_value( $value );
				$key = sprintf( '%s_%s', $key, implode( '_', $keys ) );
			}

			update_metadata( $this->get_meta_type(), $id, $key, $value );
		}
	}