"consume the generator"?

Despite the comment, I don't understand the purpose of the last line in the following excerpt from the Axes.plot() method:

         lines = []
         for line in self._get_lines(*args, **kwargs):
             self.add_line(line)
             lines.append(line)
         lines = [line for line in lines] # consume the generator

Would someone enlighten me, please? Or is that line in fact as useless as it appears to me?

Thanks.

Eric