Check if there are any pending scheduled actions due to run.
	 *
	 * @param ActionScheduler_Action $action
	 * @param DateTime $scheduled_date (optional)
	 * @return string
	 */
	public function has_pending_actions_due() {
		$pending_actions = $this->query_actions( array(
			'date'    => as_get_datetime_object(),
			'status'  => ActionScheduler_Store::STATUS_PENDING,
			'orderby' => 'none',
		) );

		return ! empty( $pending_actions );
	}

	/**
	 * Callable initialization function optionally overridden in derived classes.
	 */
	public function init() {}

	/**
	 * Callable function to mark an action as migrated optionally overridden in derived classes.
	 */
	public function mark_migrated( $action_id ) {}

	/**
	 * @return ActionScheduler_Store
	 */
	public static function instance() {
		if ( empty( self::$store ) ) {
			$class = apply_filters( 'action_scheduler_store_class', self::DEFAULT_CLASS );
			self::$store = new $class();
		}
		return self::$store;
	}
}