'Stash some states. This is an alias for move(), with defaults for the stashes.
:param filter_func: Stash states that match this filter. Should be a function. that takes a state and returns True
or False. (default: stash all states)
:param from_stash:  Take matching states from this stash. (default: \'active\')
:param to_stash:    Put matching states into this stash. (default: \'stashed\')
:returns:           The resulting SimulationManager
:rtype:             SimulationManager'

def stash(self, filter_func=None, from_stash=None, to_stash=None):

    to_stash = ('stashed' if (to_stash is None) else to_stash)
    from_stash = ('active' if (from_stash is None) else from_stash)
    return self.move(from_stash, to_stash, filter_func=filter_func)
