'Return the size of the `queue`.
Arguments:
queue (str): The name of the queue.'

def _size(self, queue):

    with self._queue_lock(queue):
        size = 0
        try:
            key = self._key_prefix(queue)
            logger.debug(u'Fetching    key    recursively    %s    with    index    %s', key, self.index)
            result = self.client.read(key=key, recursive=True, index=self.index)
            size = len(result._children)
        except TypeError:
            pass
        logger.debug(u'Found    %s    keys    under    %s    with    index    %s', size, key, self.index)
        return size
