code: def helper_parallel_lines(start0, end0, start1, end1, filename):
      
      if NO_IMAGES:
          return
  
      figure = plt.figure()
      ax = figure.gca()
      points = stack1d(start0, end0, start1, end1)
      ax.plot(points[0, :2], points[1, :2], marker="o")
      ax.plot(points[0, 2:], points[1, 2:], marker="o")
      ax.axis("scaled")
      _plot_helpers.add_plot_boundary(ax)
      save_image(figure, filename)
docs: Image for :func:`.parallel_lines_parameters` docstring.