def enumerate_ground_sensors(bones):
    bone = bones.get('GroundSensor.Axle.Ft')
    if bone is not None:
        yield bone
        for bone in bones:
            if bone.name.startswith('GroundSensor.Ft'):
                yield bone
    bone = bones.get('GroundSensor.Axle.Bk')
    if bone is not None:
        yield bone
        for bone in bones:
            if bone.name.startswith('GroundSensor.Bk'):
                yield bone