<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_viewup(self, vector):
 """ sets camera viewup vector """

        if isinstance(vector, np.ndarray):
            if vector.ndim != 1:
                vector = vector.ravel()
        self.camera.SetViewUp(vector)
        self._render()