def _draw_sentence(self):
        """Draw the sentence string."""
        if self._chart.num_leaves() == 0: return
        c = self._sentence_canvas
        margin = ChartView._MARGIN
        y = ChartView._MARGIN

        for i, leaf in enumerate(self._chart.leaves()):
            x1 = i * self._unitsize + margin
            x2 = x1 + self._unitsize
            x = (x1+x2)/2
            tag = c.create_text(x, y, text=repr(leaf),
                                font=self._font,
                                anchor='n', justify='left')
            bbox = c.bbox(tag)
            rt=c.create_rectangle(x1+2, (ChartView._LEAF_SPACING/2)-bbox[1],
                                  x2-2, bbox[3]+(ChartView._LEAF_SPACING/2),
                                  fill='#f0f0f0', outline='#f0f0f0')
            c.tag_lower(rt)
dataset/ETHPy150Open nltk/nltk/nltk/app/chartparser_app.py/ChartView._draw_sentence/swapped operands of `-`