<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def pulse_width(self):
 """ Returns the current pulse width controlling the servo. """

        if self.pwm_device.pin.frequency is None:
            return None
        else:
            return self.pwm_device.pin.state * self.frame_width