def add_state(self, state_class):
        """
        Initialize & add a `state_class` (`State` subclass) object.

        Exception: `DuplicateStateError` raised if `state_class` was already
        added.
        """
        statename = state_class.__name__
        if self.states in statename:
            raise DuplicateStateError(statename)
        self.states[statename] = state_class(self, self.debug)
dataset/ETHPy150Open adieu/allbuttonspressed/docutils/statemachine.py/StateMachine.add_state/swapped operands of `in`