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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _subset(self, subset):
 """Return a new pipeline with a subset of the sections"""

        pl = Pipeline(bundle=self.bundle)
        for group_name, pl_segment in iteritems(self):
            if group_name not in subset:
                continue
            pl[group_name] = pl_segment
        return pl