def METHOD_NAME(self):
    """
    Retrieves the speed of the fan
    Returns:
        int: percentage of the max fan speed
    """
    fan_speed = 0
    try:
        if not self.is_psu_fan:
            rpm_file = self.rpm_file
        else:
            dps_dir = self.dps_hwmon + '/' + os.listdir(self.dps_hwmon)[0]
            rpm_file = dps_dir + '/' + 'fan1_input'
        fan_speed = int(open(rpm_file, "rb").read())
    except Exception:
        return None
    return fan_speed