sprint2

is-implemented.js
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			'use strict';

			var validTypes = { object: true, symbol: true };

			module.exports = function () {
			var symbol;
			if (typeof Symbol !== 'function') return false;
			symbol = Symbol('test symbol');
			try { String(symbol); } catch (e) { return false; }

			// Return 'true' also for polyfills
			if (!validTypes[typeof Symbol.iterator]) return false;
			if (!validTypes[typeof Symbol.toPrimitive]) return false;
			if (!validTypes[typeof Symbol.toStringTag]) return false;

			return true;
			};