def inference(self, observed_arr):
        '''
        Draws samples from the `true` distribution.

        Args:
            observed_arr:     `np.ndarray` of observed data points.
        
        Returns:
            `np.ndarray` of inferenced.
        '''
        if observed_arr.ndim < 4:
            # Add rank for channel.
            observed_arr = np.expand_dims(observed_arr, axis=1)
            self.__add_channel_flag = True
        else:
            self.__add_channel_flag = False

        return super().inference(observed_arr)
Draws samples from the `true` distribution.

        Args:
            observed_arr:     `np.ndarray` of observed data points.
        
        Returns:
            `np.ndarray` of inferenced.