def METHOD_NAME(self):
    """
    Return the canonical label of ``self``.
    EXAMPLES::
        sage: P = species.SubsetSpecies()
        sage: S = P.structures(["a", "b", "c"])
        sage: [s.canonical_label() for s in S]
        [{}, {'a'}, {'a'}, {'a'}, {'a', 'b'}, {'a', 'b'}, {'a', 'b'}, {'a', 'b', 'c'}]
    """
    rng = list(range(1, len(self._list) + 1))
    return self.__class__(self.parent(), self._labels, rng)