code: function(sel) {
        if (!this.length) {
          return this;
        }
        var parents = [],
            finished = false,
            currentElement = this[0];
  
        while (!finished) {
          currentElement = currentElement.parentNode;
          if (currentElement) {
            if (sel === undefined) {
              parents.push(currentElement);
            }
            else if (u(currentElement).is(sel)) {
              parents.push(currentElement);
            }
          }
          else {
            finished = true;
          }
        }
        return u(parents);
      }
docs: parents method
  get the parent elements
  @return {object} element