_threshold setting.
	 *
	 * @return string
	 */
	public function get_level_threshold(): string {
		$key = self::PREFIX . 'level_threshold';

		$threshold = Constants::get_constant( 'WC_LOG_THRESHOLD' );

		if ( is_null( $threshold ) ) {
			$threshold = WC_Admin_Settings::get_option( $key );
		}

		if ( ! WC_Log_Levels::is_valid_level( $threshold ) ) {
			$threshold = self::DEFAULTS['level_threshold'];
		}

		return $threshold;
	}
}