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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_task_bt(self, filename, select=False):
 """ Add a new BT task :param str filename: path to torrent file to upload :param bool select: whether to select files in the torrent. * True: it returns the opened torrent (:class:`.Torrent`) and can then iterate files in :attr:`.Torrent.files` and select/unselect them before calling :meth:`.Torrent.submit` * False: it will submit the torrent with default selected files """

        filename = eval_path(filename)
        u = self.upload(filename, self.torrents_directory)
        t = self._load_torrent(u)
        if select:
            return t
        return t.submit()