Method prepend

source/python.js:8878–8883

(x)

                return this._next;
            }
            prepend(x) {
                x._remove_from_list();
                const p = this._prev;
                [p._next, x._prev] = [x, p];
                [x._next, this._prev] = [this, x];
            }
            _remove_from_list() {
                const [p, n] = [this._prev, this._next];
                [p._next, n._prev] = [n, p];