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

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()
            ) + ")"