code: def addPrefs(self, prefs=[]):
          
          if len(prefs) == len(self.preferences) == 0:
              logger.debug("no preferences")
              return None
          self.preferences.extend(prefs)
          self.css1(path['search-btn']).click()
          count = 0
          for pref in self.preferences:
              self.css1(path['search-pref']).fill(pref)
              self.css1(path['pref-icon']).click()
              btn = self.css1('div.add-to-watchlist-popup-item .icon-wrapper')
              if not self.css1('svg', btn)['class'] is None:
                  btn.click()
                  count += 1
              # remove window
              self.css1(path['pref-icon']).click()
          # close finally
          self.css1(path['back-btn']).click()
          self.css1(path['back-btn']).click()
          logger.debug("updated %d preferences" % count)
          return self.preferences
docs: add preference in self.preferences