/**
 * Calls `unref` on a timer, if the method is available on @param timer.
 *
 * `unref()` is used to allow processes to exit immediately, even if the timer
 * is still running and hasn't resolved yet.
 *
 * Use this in places where code can run on browser or server, since browsers
 * do not support `unref`.
 */
export declare function safeUnref(timer: ReturnType<typeof setTimeout>): ReturnType<typeof setTimeout>;
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