Get a playlist from it's ID

        :param playlist_id: ID of the playlist
        :rtype: a :class:`Playlist` object

def playlist(self, playlist_id):
        '''
        Get a playlist from it's ID

        :param playlist_id: ID of the playlist
        :rtype: a :class:`Playlist` object
        '''
        playlist = self.connection.request(
            'getPlaylistByID',
            {'playlistID': playlist_id},
            self.connection.header('getPlaylistByID'))[1]
        return self._parse_playlist(playlist)