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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 get_channel_access_token(self, channel):
 """Return the token and sig for the given channel :param channel: the channel or channel name to get the access token for :type channel: :class:`channel` | :class:`str` :returns: The token and sig for the given channel :rtype: (:class:`unicode`, :class:`unicode`) :raises: None """

        if isinstance(channel, models.Channel):
            channel = channel.name
        r = self.oldapi_request(
            'GET', 'channels/%s/access_token' % channel).json()
        return r['token'], r['sig']