'Return the number of messages in `queue` as an :class:`int`.'

def _size(self, queue):

    count = 0
    queue_find = u'.{0}.msg'.format(queue)
    folder = os.listdir(self.data_folder_in)
    while (len(folder) > 0):
        filename = folder.pop()
        if (filename.find(queue_find) < 0):
            continue
        count += 1
    return count
