def METHOD_NAME(self):
    """
    Retrieves the speed of fan as a percentage of full speed
    Returns:
        An integer, the percentage of full fan speed, in the range 0 (off)
             to 100 (full speed)
    Note:
        speed = pwm_in/255*100
    """
    speed = 0
    fan_speed_sysfs_name = "fan{}_input".format(self.fan_index+1)
    fan_speed_sysfs_path = self.__search_file_by_name(
        FAN_PATH.format(self.fan_tray_index + 1), fan_speed_sysfs_name)
    fan_speed_rpm = self.__read_txt_file(fan_speed_sysfs_path) or 0
    speed = math.ceil(float(fan_speed_rpm) * 100 / FAN_MAX_RPM)
    return int(speed)