docs: function Stash(nlz) {
    if (!(this instanceof Stash)) return new Stash(nlz);
  
    nlz = nlz || function(val) {return val};
    assert.equal(typeof nlz, 'function', 'linkstash: nlz should be a function');
  
    this._prev = null;
    this._next = null;
    this._nlz = nlz;
  
    return this;
  }