def _dequeue(self):
        """Internal method; returns the first available line out of the
        cache, if any."""
        if len(self.queue) > 0:
            line = self.queue[0]
            self.queue = self.queue[1:]
            return line
        else:
            return None
Internal method; returns the first available line out of the
        cache, if any.
recipes/Python/436477_filetailpy/recipe-436477.py