<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_X(self, X):
 """ Set the input data of the model :param X: input observations :type X: np.ndarray """

        assert isinstance(X, np.ndarray)
        state = self.update_model()
        self.update_model(False)
        self.X = ObsAr(X)
        self.update_model(state)