Custom Jar files not showing in SmartDashboard

[xmendude217]

Im trying to use the WPILib Cookbook's example for getting vision tracking done the SmartDashboard, yet whenever I build the jar and place it in the SmartDashboard's extension folder, I can't see it in the SmartDashboard's "Add" submenu. Here's the code for the jar :

public class VisionSystem extends WPICameraExtension {
    @Override
    public WPIImage processImage(WPIColorImage rawImage) {
        return rawImage.getBlueChannel();
         }
}