docs: public Transition<S> getTransition(S fromState, T transition){
  		Transition<S> transitionDef = transitions.get(new DoubleValueBean<S, T>(fromState, transition));
  		if (transitionDef == null){
  			throw new IllegalArgumentException("Transition '" + transition + "' from state '" + fromState + "' has not been defined.");
  		}
  		return transitionDef;
  	}