CODING CONVENTIONS

1. write your methods always in the following order:

    extTransition
    timeAdvance
    outputFnc
    intTransition

  this reflects the order in which the methods are called by the simulator:

     extTransition always has highest priority (can interrupt anything)
     timeAdvance is called before outputFnc
     outputFnc is called right before intTransition


2. input/output port attributes start with 'in_' and 'out_'


TROUBLESHOOTING

  - did you forget to return `self.state` from intTransition or extTransition ?
  - did you accidentally write to `self.x` instead of `self.state.x` ?
  - did you modify the state in timeAdvance or outputFnc (NOT ALLOWED!!)