count people in a room, switch on the light if anybody in the room, and switch off if nobody in the room

bool isRoomEmpty(List<Person> people) {
  return people.isEmpty();
}

void turnOnLight() {
  Light.brightness = 100;
}

void turnOffLight() {
  Light.brightness = 0;
}

void switchLight(List<Person> people) {
  if (isRoomEmpty(people)) {
    turnOffLight();
  } else {
    turnOnLight();
  }
}