docs: def zap_horizontally(can, style, pat, x1, y1, x2, y2, xsize, ysize):
      """Draw a horizontal "zapping" symbol on the canvas that shows
      that a graph is ripped in the middle.
  
      Parameter <fill_style> specifies the style for the zig-zag lines.
      PAT specifies the pattern with which the area is filled.
      The symbol is drawn in the rectangle (<x1>, <y1>) - (<x2>, <y2>).
      Each "zigzag" has the width <xsize>, height <ysize>."""
  
      assert isinstance(style, line_style.T)
      assert isinstance(pat, fill_style.T)
  
      points = []
      points2 = []
      x = x1
      y = y1
      while x < x2:
          points.append((x, y))
          points2.append((x, y + (y2 - y1)))
          x += xsize
          if y == y1:
              y += ysize
          else:
              y -= ysize
  
      points2.reverse()
      _draw_zap(can, points, points2, style, pat)