<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def initialState(self, state):
 """ Set this automaton's initial state. Raises a ValueError if this automaton already has an initial state. """


        if self._initialState is not _NO_STATE:
            raise ValueError(
                "initial state already set to {}".format(self._initialState))

        self._initialState = state