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)))