<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get(self, aspect):
 """Get a network, system or configure or contextualize with the same id as aspect passed."""


        classification = [(network, self.networks), (system, self.systems),
                          (configure, self.configures)]
        aspect_list = [l for t, l in classification if isinstance(aspect, t)]
        assert len(aspect_list) == 1, "Unexpected aspect for RADL."
        aspect_list = aspect_list[0]

        old_aspect = [a for a in aspect_list if a.getId() == aspect.getId()]
        return old_aspect[0] if old_aspect else None