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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 _update_labels(self, label, crop_box, height, width):
 """Convert labels according to crop box"""

        xmin = float(crop_box[0]) / width
        ymin = float(crop_box[1]) / height
        w = float(crop_box[2]) / width
        h = float(crop_box[3]) / height
        out = label.copy()
        out[:, (1, 3)] -= xmin
        out[:, (2, 4)] -= ymin
        out[:, (1, 3)] /= w
        out[:, (2, 4)] /= h
        out[:, 1:5] = np.maximum(0, out[:, 1:5])
        out[:, 1:5] = np.minimum(1, out[:, 1:5])
        coverage = self._calculate_areas(out[:, 1:]) * w * h / self._calculate_areas(label[:, 1:])
        valid = np.logical_and(out[:, 3] > out[:, 1], out[:, 4] > out[:, 2])
        valid = np.logical_and(valid, coverage > self.min_eject_coverage)
        valid = np.where(valid)[0]
        if valid.size < 1:
            return None
        out = out[valid, :]
        return out