def display_boxes(self, pdf_file, boxes, alternate_colors=False):
        """
        Displays each of the bounding boxes passed in 'boxes' on images of the pdf
        pointed to by pdf_file
        boxes is a list of 5-tuples (page, top, left, bottom, right)
        """
        imgs = []
        colors = [Color("blue"), Color("red")]
        boxes_per_page = defaultdict(int)
        boxes_by_page = defaultdict(list)
        for i, (page, top, left, bottom, right) in enumerate(boxes):
            boxes_per_page[page] += 1
            boxes_by_page[page].append((top, left, bottom, right))
        for i, page_num in enumerate(boxes_per_page.keys()):
            img = pdf_to_img(pdf_file, page_num)
            draw = Drawing()
            draw.fill_color = Color("rgba(0, 0, 0, 0.0)")
            for j, (top, left, bottom, right) in enumerate(boxes_by_page[page_num]):
                draw.stroke_color = colors[j % 2] if alternate_colors else colors[0]
                draw.rectangle(left=left, top=top, right=right, bottom=bottom)
            draw(img)
            imgs.append(img)
        return imgs
Displays each of the bounding boxes passed in 'boxes' on images of the pdf
        pointed to by pdf_file
        boxes is a list of 5-tuples (page, top, left, bottom, right)