docs: function transition() {
      var ts = this.__transitions__, i, len;
  
      if (!ts || ts.length === 0) { return; }
  
      for (i = 0, len = ts.length; i < len; i++) {
        enter.call(ts[i].pivot, ts[i].states, ts[i].opts);
      }
  
      this.__transitions__ = [];
    }