Adds a Bus object to the case.

def push_bus(self, tokens):
        """ Adds a Bus object to the case.
        """
        logger.debug("Pushing bus data: %s" % tokens)

        bus = Bus()
        bus.name = tokens["bus_no"]
        bus.v_magnitude = tokens["v_magnitude"]
        bus.v_angle = tokens["v_angle"]
        bus.v_magnitude = tokens["v_magnitude"]
        bus.v_angle = tokens["v_angle"]

        self.case.buses.append(bus)