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

def drop(self, filter_func=None, stash=None):

    stash = ('active' if (stash is None) else stash)
    return self.move(stash, self.DROP, filter_func=filter_func)
