docs: def draw_arith(ax, p0, size=1, alpha=0, arith=None, format=None,
                 fontsize=10, **kwds):
      r"""Draw an arithmetic operator."""
      if format is None: format = 'k-'
      a = size/2.0
      x0 = [0, 2.5*a, 0, 0]
      y0 = [a, 0, -a, a]
  
      cur_list = [(x0, y0)]
      cur_list = rotate_and_traslate(cur_list, alpha, p0)
  
      for curi in cur_list: ax.plot(curi[0], curi[1], format, **kwds)
  
      if arith is not None:
          pyplot.text(p0[0]+0.75*a, p0[1], arith, horizontalalignment='center',
                      verticalalignment='center', fontsize=fontsize)