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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 path(self):
 """The path attribute returns a stringified, concise representation of the MultiFieldSelector. It can be reversed by the ``from_path`` constructor. """

        if len(self.heads) == 1:
            return _fmt_mfs_path(self.heads.keys()[0], self.heads.values()[0])
        else:
            return "(" + "|".join(
                _fmt_mfs_path(k, v) for (k, v) in self.heads.items()
            ) + ")"