/**
 * Converts a human-readable time string to milliseconds.
 * Supports units: `ms`, `s`, `m`, `h`, `d`. If a number is passed, it is returned as-is.
 *
 * @param time - A time string (e.g. `"500ms"`, `"1.5s"`, `"2h"`) or a numeric millisecond value
 * @returns The time in milliseconds, or `undefined` if `time` is falsy
 * @throws Error if the string format is invalid
 *
 * @example
 * ```ts
 * inMs("2s")   // 2000
 * inMs("1.5h") // 5400000
 * inMs(500)    // 500
 * ```
 */
export declare const inMs: (time?: string | number) => number | undefined;