docs: def m_seg(p1, p2, rad, dist):
      """ move segment by distance
      Args:
        p1, p2: point(x, y)
        rad: relative direction angle(radian)
        dist: distance
      Return:
        translated segment(p1, p2)
      """
      v = vector(p1, p2)
      m = unit(rotate(v, rad), dist)
      return translate(p1, m), translate(p2, m)