docs: async def add_items(self, *items):
      '''append items to the playlist
  
      |coro|
  
      Parameters
      ----------
      items : array_like
        list of items to add(or their ids)
  
      See Also
      --------
        remove_items :
      '''
      items = [item.id for item in await self.process(items)]
      if not items:
        return
  
      await self.connector.post('Playlists/{Id}/Items'.format(Id=self.id),
        data={'Ids': ','.join(items)}, remote=False
      )