gistfile1.txt

class StateGuard(type):
    def __new__(cls, name, bases, dct):
        base_states = [base for base in bases if type(base) == cls]
        if len(base_states) > 1:
            raise TypeError("Multiple inheritance of States is not allowed")
        elif len(base_states) == 1:
            state = base_states.pop()
            state_methods = {method for method in dir(state) if not method.startswith('__')}
            for b in bases:
                if b == state:
                    continue
                base_methods = {method for method in dir(b) if not method.startswith('__')}
                overrides = base_methods & state_methods
                if overrides:
                    raise TypeError(f'Class {b} overrides methods {overrides} from {state}. This is not allowed')
        return super().__new__(cls, name, bases, dct)
class BaseState(metaclass=StateGuard):