docs: def beam_splitter(ax, p0, size=2.54, alpha=0, format=None, **kwds):
      r"""Draw a beam splitter."""
      if format is None: format = 'k-'
      a = size/2
      x0 = [a, -a, -a, a, a, -a]
      y0 = [a, a, -a, -a, 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)