Embodiments of a testcase checker system are disclosed herein. A carbon nanotube composition comprising carbon nanotubes and a metal component selected from the group consisting of metal nanoparticles and elemental metal; wherein the carbon nanotube composition is rigid. As the vehicle’s tires rotate, wind passes across the whistle, which in turn produces sound that is audible to animals and in turn alerts animals of the oncoming traffic. A method for assembling the lens module is also provided. A solar cell string and a solar cell module employ the solar cells.