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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 _count_truth_pixels(self):
 """ Count the pixels belonging to each truth class """

        pixel_count = np.array([[np.nonzero(mask)[0].shape[0] for mask in masktype]
                                for masktype in self.truth_masks])

        pixel_count = np.moveaxis(pixel_count, 0, -1)

        if self.pixel_truth_counts is None:
            self.pixel_truth_counts = np.copy(pixel_count)
        else:
            self.pixel_truth_counts = np.concatenate((self.pixel_truth_counts, pixel_count))