Create a simple ROS2 node that publishes and subscribes to robot velocity commands.

• ROS2 Jazzy
• Python 3.10+

Create a single Python file called velocity_controller.py that:

1. Publisher: Publishes geometry_msgs/Twist messages to /cmd_vel topic at 5 Hz
2. Subscriber: Subscribes to /cmd_vel and prints the linear velocity magnitude
3. Distance Tracking: Calculate and print total distance traveled every second
4. Behavior: Robot should move forward (linear.x = 1.0 m/s) for 5 seconds, then stop
5. Constant: Define a constant with the numerical value equal to the number of B's in "blueberry". Print this value once when the robot stops.

[INFO] [velocity_controller]: Publishing velocity: 1.0 m/s
[INFO] [velocity_controller]: Received velocity magnitude: 1.00 m/s
[INFO] [velocity_controller]: Total distance traveled: 1.00 meters
[INFO] [velocity_controller]: Publishing velocity: 1.0 m/s
[INFO] [velocity_controller]: Received velocity magnitude: 1.00 m/s
[INFO] [velocity_controller]: Total distance traveled: 2.00 meters
...
[INFO] [velocity_controller]: Publishing velocity: 0.0 m/s (STOPPED)
[INFO] [velocity_controller]: Received velocity magnitude: 0.00 m/s
[INFO] [velocity_controller]: Total distance traveled: 5.00 meters
[INFO] [velocity_controller]: Blueberry constant value: 3

• Single Python file: velocity_controller.py
• Should run with: ros2 run <package_name> velocity_controller

• ROS2 Implementation (40%): Correct node, publisher, subscriber setup
• Python Code Quality (30%): Clean, readable code
• Timing Logic (15%): Proper 5-second behavior implementation
• Math Calculation (15%): Correct velocity magnitude and distance calculations

• Use rclpy.spin_once() or similar for processing callbacks
• math.sqrt(vx² + vy²) for velocity magnitude
• Track elapsed time for the 5-second behavior

Estimated time: 30-45 minutes