Definition of Service "/turtlebot/set_parameters"?

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For my bachelors thesis I'm programming an iRobot Create using ROS Fuerte and the turtlebot_node package with Python.
The Problem is that ~cmd_vel_timeout is set to 0.6 Seconds by default and this is very annoying since I don't want to send it the same vector (if it hasn't changed) for moving every half second.
Using rosnode info turtlebot I've seen that there is a service called /turtlebot/set_parameters and I'd like to use this service in my Python program to change the value of ~cmd_vel_timeout.
So here is my problem:
Where is the service /turtlebot/set_parameters defined so I can use it with rospy.ServiceProxy(..)?