code: function _setCollectionFrom(COLLECTION) {
  	  _export(_export.S, COLLECTION, { from: function from(source /* , mapFn, thisArg */) {
  	      var mapFn = arguments[1];
  	      var mapping, A, n, cb;
  	      _aFunction(this);
  	      mapping = mapFn !== undefined;
  	      if (mapping) _aFunction(mapFn);
  	      if (source == undefined) return new this();
  	      A = [];
  	      if (mapping) {
  	        n = 0;
  	        cb = _ctx(mapFn, arguments[2], 2);
  	        _forOf(source, false, function (nextItem) {
  	          A.push(cb(nextItem, n++));
  	        });
  	      } else {
  	        _forOf(source, false, A.push, A);
  	      }
  	      return new this(A);
  	    } });
  	}
docs: https://tc39.github.io/proposal-setmap-offrom/