def get_lcstate_predecessors(self, some_state):
        if some_state and "_" in some_state:
            raise BadRequest("Compound lcstates are obsolete")
        return {src: evt for (src, evt), targ in self.lcstate_transitions.iteritems() if targ == some_state}
For a given state, return a dict of possible predecessor states => the transition to move
dataset/ETHPy150Open ooici/pyon/pyon/ion/resource.py/ResourceLifeCycleSM.get_lcstate_predecessors