debug.drawline not working unity code example

Example: debug.drawline unity

Debug.DrawLine(Vector3 a,Vector3 b);
Debug.DrawLine(Vector3 a,Vector3 b, Color color);
Debug.DrawLine(Vector3 a,Vector3 b, Color color, float duration);
Debug.DrawLine(Vector3 a,Vector3 b, Color color, float duration, bool depthTest);