from sympy.abc import s
from sympy import I
from sympy.physics.control.lti import TransferFunction
from spb import plot_pole_zero
tf1 = TransferFunction(
    s**2 + 1, s**4 + 4*s**3 + 6*s**2 + 5*s + 2, s)
plot_pole_zero(tf1, sgrid=True)