def __init__ ( self, *traits, **metadata ):
        self.trait_maker = _TraitMaker( metadata.pop( 'default', None ),
                                        *traits, **metadata )
set self._citekeys to keys **and** make associated entries
dataset/ETHPy150Open enthought/traits/traits/trait_types.py/Either.__init__--crossover with--dataset/ETHPy150Open dschwilk/bibstuff/bibstuff/bibstyles/shared.py/CitationManager.set_citekeys