Error in jetbot code

I try to run jetboat even if I imported modules I got this below error

error

OSErrorTraceback (most recent call last)
in
----> 1 robot = Robot()

/usr/local/lib/python3.6/dist-packages/jetbot-0.4.1-py3.6.egg/jetbot/robot.py in init(self, *args, **kwargs)
20 def init(self, *args, **kwargs):
21 super(Robot, self).init(*args, **kwargs)
—> 22 self.motor_driver = Adafruit_MotorHAT(i2c_bus=self.i2c_bus)
23 self.left_motor = Motor(self.motor_driver, channel=self.left_motor_channel, alpha=self.left_motor_alpha)
24 self.right_motor = Motor(self.motor_driver, channel=self.right_motor_channel, alpha=self.right_motor_alpha)

/usr/local/lib/python3.6/dist-packages/Adafruit_MotorHAT-1.4.0-py3.6.egg/Adafruit_MotorHAT/Adafruit_MotorHAT_Motors.py in init(self, addr, freq, i2c, i2c_bus)
229 self.motors = [ Adafruit_DCMotor(self, m) for m in range(4) ]
230 self.steppers = [ Adafruit_StepperMotor(self, 1), Adafruit_StepperMotor(self, 2) ]
–> 231 self._pwm = PWM(addr, debug=False, i2c=i2c, i2c_bus=i2c_bus)
232 self._pwm.setPWMFreq(self._frequency)
233