Model order reduction of a transfer function

def order_reduction(H, n):
  """
  Model order reduction of a transfer function H(s) using the
  balanced truncation method.

  Inputs:
  H: transfer function
  n: order of reduced model

  Outputs:
  Hred: reduced model
  """
  # Compute the Hankel singular values of H
  sigma = np.linalg.svd(