docs: def p_seg(p1, p2, cw, interval, trim=0, align=0):
      """ parallel segment
      Args:
        p1, p2: point(x, y)
        cw: m_seg rad True: -π/2, False: π/2
        interval: m_seg dist
        trim: t_seg trim
        align: t_seg align
      """
      case = {True: pi / -2, False: pi / 2}
      p1m, p2m = m_seg(p1, p2, case[cw], interval)
      return t_seg(p1m, p2m, trim, align)