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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 origin(self):
 """Show where the 'origin' remote ref points. Returns None if the 'origin' remote ref does not exist. If 'origin' has different locations for different commands, the result is ambiguous and None is returned. Notes: A repo does not necessarily have any remotes configured. A repo with remotes configured does not necessarily have an 'origin' remote ref. This property is for common convenience. """

        remotes = self.list_remotes()
        candidates = set()
        for remote_ref in remotes:
            if remote_ref['name'] == 'origin':
                candidates.add(remote_ref['location'])
        if len(candidates) == 1:
            return candidates.pop()