How to use the pymavlink.mavutil.mavlink.MAV_CMD_CONDITION_YAW function in pymavlink

By default the yaw of the vehicle will follow the direction of travel. After setting 
    the yaw using this function there is no way to return to the default yaw "follow direction 
    of travel" behaviour (https://github.com/diydrones/ardupilot/issues/2427)

    For more information see: 
    http://copter.ardupilot.com/wiki/common-mavlink-mission-command-messages-mav_cmd/#mav_cmd_condition_yaw
    """
    if relative:
        is_relative = 1 #yaw relative to direction of travel
    else:
        is_relative = 0 #yaw is an absolute angle
    # create the CONDITION_YAW command using command_long_encode()
    msg = vehicle.message_factory.command_long_encode(
        0, 0,       # target system, target component
        mavutil.mavlink.MAV_CMD_CONDITION_YAW, #command
        0,          #confirmation
        heading,    # param 1, yaw in degrees
        0,          # param 2, yaw speed deg/s
        1,          # param 3, direction -1 ccw, 1 cw
        is_relative, # param 4, relative offset 1, absolute angle 0
        0, 0, 0)    # param 5 ~ 7 not used
    # send command to vehicle
    vehicle.send_mavlink(msg)

def cmd_condition_yaw(self, args):
        '''yaw angle angular_speed angle_mode'''
        if ( len(args) != 3):
            print("Usage: yaw ANGLE ANGULAR_SPEED MODE:[0 absolute / 1 relative]")
            return

        if (len(args) == 3):
            angle = float(args[0])
            angular_speed = float(args[1])
            angle_mode = float(args[2])
            print("ANGLE %s" % (str(angle)))
            self.master.mav.command_long_send(
                self.settings.target_system,  # target_system
                mavutil.mavlink.MAV_COMP_ID_SYSTEM_CONTROL, # target_component
                mavutil.mavlink.MAV_CMD_CONDITION_YAW, # command
                0, # confirmation
                angle, # param1 (angle value)
                angular_speed, # param2 (angular speed value)
                0, # param3
                angle_mode, # param4 (mode: 0->absolute / 1->relative)
                0, # param5
                0, # param6
                0) # param7

def condition_yaw(heading):
    msg = vehicle.message_factory.mission_item_encode(0, 0,  # target system, target component
            0,     # sequence
            mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT, # frame
            mavutil.mavlink.MAV_CMD_CONDITION_YAW,         # command
            2, # current - set to 2 to make it a guided command
            0, # auto continue
            heading,    # param 1, yaw in degrees
            0,          # param 2, yaw speed deg/s
            1,          # param 3, direction -1 ccw, 1 cw
            0,          # param 4, relative offset 1, absolute angle 0
            0, 0, 0)    # param 5 ~ 7 not used
    # send command to vehicle
    vehicle.send_mavlink(msg)
    vehicle.flush()

By default the yaw of the vehicle will follow the direction of travel. After setting 
    the yaw using this function there is no way to return to the default yaw "follow direction 
    of travel" behaviour (https://github.com/diydrones/ardupilot/issues/2427)

    For more information see: 
    http://copter.ardupilot.com/wiki/common-mavlink-mission-command-messages-mav_cmd/#mav_cmd_condition_yaw
    """
    if relative:
        is_relative = 1 #yaw relative to direction of travel
    else:
        is_relative = 0 #yaw is an absolute angle
    # create the CONDITION_YAW command using command_long_encode()
    msg = vehicle.message_factory.command_long_encode(
        0, 0,    # target system, target component
        mavutil.mavlink.MAV_CMD_CONDITION_YAW, #command
        0, #confirmation
        heading,    # param 1, yaw in degrees
        0,          # param 2, yaw speed deg/s
        1,          # param 3, direction -1 ccw, 1 cw
        is_relative, # param 4, relative offset 1, absolute angle 0
        0, 0, 0)    # param 5 ~ 7 not used
    # send command to vehicle
    vehicle.send_mavlink(msg)

if self.vehicle.mount_status[0] is not None:
            pointingMsg = self.vehicle.message_factory.mount_control_encode(
                0, 1,             # target system, target component
                startPitch * 100, # pitch in centidegrees
                0.0,              # roll not used
                startYaw * 100,   # yaw in centidegrees
                0                 # save position
            )
            self.vehicle.send_mavlink(pointingMsg)

        # if not, assume fixed mount
        else:
            # if we don't have a gimbal, just set CONDITION_YAW
            pointingMsg = self.vehicle.message_factory.command_long_encode(
                0, 1,               # target system, target component
                mavutil.mavlink.MAV_CMD_CONDITION_YAW,  # command
                0,                  # confirmation
                startYaw,           # param 1 - target angle (degrees)
                ATTACH_YAW_SPEED,   # param 2 - yaw speed (deg/s)
                0,                  # param 3 - direction, always shortest route for now...
                0.0,                # relative offset
                0, 0, 0             # params 5-7 (unused)
            )
            self.vehicle.send_mavlink(pointingMsg)

def condition_yaw(heading):
    msg = vehicle.message_factory.mission_item_encode(0, 0,  # target system, target component
            0,     # sequence
            mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT, # frame
            mavutil.mavlink.MAV_CMD_CONDITION_YAW,         # command
            2, # current - set to 2 to make it a guided command
            0, # auto continue
            heading,    # param 1, yaw in degrees
            0,          # param 2, yaw speed deg/s
            1,          # param 3, direction -1 ccw, 1 cw
            0,          # param 4, relative offset 1, absolute angle 0
            0, 0, 0)    # param 5 ~ 7 not used
    # send command to vehicle
    vehicle.send_mavlink(msg)
    vehicle.flush()

def condition_yaw(self, heading):
        # create the CONDITION_YAW command
        msg = self.vehicle.message_factory.mission_item_encode(0, 0,  # target system, target component
                                                     0,     # sequence
                                                     mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT, # frame
                                                     mavutil.mavlink.MAV_CMD_CONDITION_YAW,         # command
                                                     2, # current - set to 2 to make it a guided command
                                                     0, # auto continue
                                                     heading, 0, 0, 0, 0, 0, 0) # param 1 ~ 7
        # send command to vehicle
        self.vehicle.send_mavlink(msg)
        self.vehicle.flush()

isRelative = 1
		else:
			isRelative = 0
			
		# The vehicle will rotate in cw or ccw by some degrees
		if clock_wise:
			direction = 1  # Degree described by 'heading' will be added to current degree
		else:
			direction = -1 # Degree described by 'heading' will be subscribed from current degree
		if not relative:
			direction = 0

		# create the CONDITION_YAW command
		msg = self.vehicle.message_factory.command_long_encode(
						0, 0,       # target system, target component
						mavutil.mavlink.MAV_CMD_CONDITION_YAW, # command
						0,          # confirmation
						heading,    # param 1, yaw in degrees
						0,          # param 2, yaw speed (not used)
						direction,  # param 3, direction
						isRelative, # param 4, relative or absolute degrees 
						0, 0, 0)    # param 5-7, not used
		# send command to vehicle
		self.vehicle.send_mavlink(msg)
		self.vehicle.flush()
		return True

def vehicle_condition_yaw(self, heading, relative=False):
        if relative:
            is_relative = 1  # yaw relative to direction of travel
        else:
            is_relative = 0  # yaw is an absolute angle
        # create the CONDITION_YAW command using command_long_encode()
        msg = self.vehicle.message_factory.command_long_encode(
                0, 0,  # target system, target component
                mavutil.mavlink.MAV_CMD_CONDITION_YAW,  # command
                0,  # confirmation
                heading,  # param 1, yaw in degrees
                0,  # param 2, yaw speed deg/s
                1,  # param 3, direction -1 ccw, 1 cw
                is_relative,  # param 4, relative offset 1, absolute angle 0
                0, 0, 0)  # param 5 ~ 7 not used

        # send command to vehicle
        self.vehicle.send_mavlink(msg)
        self.vehicle.flush()

# if we do have a gimbal, use mount_control to set pitch and yaw
        if self.vehicle.mount_status[0] is not None:
            msg = self.vehicle.message_factory.mount_control_encode(
                0, 1,    # target system, target component
                # pitch is in centidegrees
                self.camPitch * 100.0,
                0.0,  # roll
                # yaw is in centidegrees
                self.camYaw * 100.0,
                0  # save position
            )
        else:
            # if we don't have a gimbal, just set CONDITION_YAW
            msg = self.vehicle.message_factory.command_long_encode(
                0, 0,    # target system, target component
                mavutil.mavlink.MAV_CMD_CONDITION_YAW,  # command
                0,  # confirmation
                self.camYaw,  # param 1 - target angle
                YAW_SPEED,  # param 2 - yaw speed
                self.camDir,  # param 3 - direction XXX
                0.0,  # relative offset
                0, 0, 0  # params 5-7 (unused)
            )
        self.vehicle.send_mavlink(msg)