def METHOD_NAME(self):
    """
    Returns the group of permutations whose action on this set leave it
    fixed. For the species of sets, there is only one isomorphism
    class, so every permutation is in its automorphism group.
    EXAMPLES::
        sage: F = species.SetSpecies()
        sage: a = F.structures(["a", "b", "c"]).random_element(); a
        {'a', 'b', 'c'}
        sage: a.automorphism_group()
        Symmetric group of order 3! as a permutation group
    """
    from sage.groups.perm_gps.permgroup_named import SymmetricGroup
    return SymmetricGroup(max(1,len(self._labels)))