from sympy.abc import s, t
from sympy import Heaviside
from sympy.physics.control.lti import TransferFunction
from spb import *
tf1 = TransferFunction(
    8*s**2 + 18*s + 32, s**3 + 6*s**2 + 14*s + 24, s)
graphics(
    line(Heaviside(t), (t, -1, 8), label="step"),
    step_response(tf1, label="response", upper_limit=8),
    xlabel="Time [s]", ylabel="Amplitude"
)