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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def predicted_obs_vec(self):
        '''The predicted observation vector

        The observation vector for the next step in the filter.
        '''
        if not self.has_cached_obs_vec:
            self.obs_vec = dot_n(
                self.observation_matrix,
                self.predicted_state_vec[:,:,np.newaxis])[:,:,0]
        return self.obs_vec