code: def transDrift(length=0.0, gamma=None):
      
      m = np.eye(6, 6, dtype=np.float64)
      if length == 0.0:
          print("warning: 'length' should be a positive float number.")
      elif gamma is not None and gamma != 0.0:
          m[0, 1] = m[2, 3] = length
          m[4, 5] = float(length) / gamma / gamma
      else:
          print("warning: 'gamma' should be a positive float number.")
      return m
docs: Transport matrix of drift
  
      :param length: drift length in [m]
      :param gamma: electron energy, gamma value
      :return: 6x6 numpy array