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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 list(self, path=None, with_metadata=False, include_partitions=False):
 """Combine a listing of all of the upstreams, and add a metadata item for the repo_id"""


        l = {}
        for upstream in [self.alternate, self.upstream]:

            for k, v in upstream.list(path, with_metadata, include_partitions).items():
                upstreams = (l[k]['caches'] if k in l else []) + \
                    v.get('caches', upstream.repo_id)

                l[k] = v
                l[k]['caches'] = upstreams

        return l