padded(minCount, paddingItem=undefined) {
        if (minCount < 0) {
            throw new Error("needed minCount >= 0");
        }
        let seq = this._iterable;
        return Seq.fromGenerator(function*() {
            let remaining = minCount;
            for (let e of seq) {
                yield e;
                remaining -= 1;
            }
            while (remaining > 0) {
                yield paddingItem;
                remaining -= 1;
            }
        });
    }
Returns a sequence starting with the same items, but padded up to the given length with the given item. If the
sequence already exceeds the given length, no items are added.
@param {!int} minCount
@param {A=} paddingItem
@returns {!Seq.<T|A>}
@template T, A