code: def get_bookmarks(self, time=None, chan=None):
          
          # get bookmarks inside window
          try:
              bookmarks = self.rater.find('bookmarks')
          except AttributeError:
              raise IndexError('You need to have at least one rater')
  
          mrks = []
          for m in bookmarks:
  
              bookmark_start = float(m.find('bookmark_start').text)
              bookmark_end = float(m.find('bookmark_end').text)
              bookmark_chan = m.find('bookmark_chan').text
              if bookmark_chan is None:  # xml doesn't store empty string
                  bookmark_chan = ''
  
              if time is None:
                  time_cond = True
              else:
                  time_cond = (time[0] <= bookmark_end and
                               time[1] >= bookmark_start)
  
              if chan is None:
                  chan_cond = True
              else:
                  chan_cond = bookmark_chan == chan
  
              if time_cond and chan_cond:
                  one_mrk = {'name': m.find('bookmark_name').text,
                             'start': bookmark_start,
                             'end': bookmark_end,
                             'chan': bookmark_chan.split(', '),  # always a list
                             }
                  mrks.append(one_mrk)
  
          return mrks
docs: Raises
          ------
          IndexError
              When there is no selected rater