code: def ss2zpk(a,b,c,d, input=0):
      
      import scipy.signal
      z, p, k = scipy.signal.ss2zpk(a, b, c, d, input=input)
      return z, p, k
docs: State-space representation to zero-pole-gain representation.
  
      :param A: ndarray State-space representation of linear system.
      :param B: ndarray State-space representation of linear system.
      :param C: ndarray State-space representation of linear system.
      :param D: ndarray State-space representation of linear system.
      :param int input: optional For multiple-input systems, the input to use.
  
      :return:
          * z, p : sequence  Zeros and poles.
          * k : float System gain.
  
      .. note:: wrapper of scipy function ss2zpk