code: def goForward(self):
          
          if not self.canGoForward():
              return ''
          
          self._blockStack = True
          self._index += 1
          self.emitCurrentChanged()
          self._blockStack = False
          return self.currentUrl()
docs: Goes down one level if possible and returns the url at the current \
          level.  If it cannot go down, then a blank string will be returned.
          
          :return     <str>