getSteamLevels(steamids, callback) {
		return StdLib.Promises.timeoutCallbackPromise(10000, ['users'], callback, (resolve, reject) => {
			let accountids = steamids.map((steamID) => {
				if (typeof steamID === 'string') {
					return (new SteamID(steamID)).accountid;
				} else {
					return steamID.accountid;
				}
			});

			this._send(EMsg.ClientFSGetFriendsSteamLevels, {accountids}, (body) => {
				let output = {};

				let sid = new SteamID();
				sid.universe = SteamID.Universe.PUBLIC;
				sid.type = SteamID.Type.INDIVIDUAL;
				sid.instance = SteamID.Instance.DESKTOP;

				(body.friends || []).forEach((user) => {
					sid.accountid = user.accountid;
					output[sid.getSteamID64()] = user.level;
				});

				resolve({users: output});
			});
		});
	}
Gets the Steam Level of one or more Steam users.
@param {(SteamID[]|string[])} steamids - An array of SteamID objects, or strings which can parse into one.
@param {function} [callback] - Called on completion with `err`, and an object whose keys are 64-bit SteamIDs as strings, and whose values are Steam Level numbers.
@return {Promise}