Dronekit python commands

I am using pixhawk and Raspberry pi 3 for autonomous landing. I want to use my own algorithm for landing. I could install dronekit in Rpi 3 and run the python scripts and get heart beat and vehicle states. I want to give attitude commands from Rpi 3 to pixhawk . What are the commands i have to use and in which mode i hve to send commands to pixhawk. I tried command.override and checked it by connecting servos to pixhawk. When i run the python code in RPi3 servo movements instantaneous. I dont know how to check the command sent to pixhawk. Is there any other method to test the s/w other than SITL?