text: import math
  
  
  # ----Auxiliary function for transformations so and se ----
  
  
  def mod_pipi(alpha):
      """
      mod_pipi(alpha) \n
      :param alpha: angle in rad
      :return: equivalent alpha in (-pi, pi]
      """
      if alpha > 2 * math.pi:
          alpha %= (2 * math.pi)
      elif alpha < -2 * math.pi:
          alpha %= (-2 * math.pi)
  
      if alpha > math.pi:
          alpha -= 2 * math.pi
      elif alpha <= -math.pi:
          alpha += 2 * math.pi
  
      return alpha
  