docs: def check_if_outcome_already_connected(self, from_state_id, from_outcome):
          """ check if outcome of from state is not already connected
  
          :param from_state_id: The source state of the transition
          :param from_outcome: The outcome of the source state to connect the transition to
          :raises exceptions.AttributeError: if the outcome of the state with the state_id==from_state_id
                                              is already connected
          """
          for trans_key, transition in self.transitions.items():
              if transition.from_state == from_state_id:
                  if transition.from_outcome == from_outcome:
                      raise AttributeError("Outcome %s of state %s is already connected" %
                                           (str(from_outcome), str(from_state_id)))