code: def cross_v3(vec_a, vec_b):
      
  
      return Vec3(vec_a.y * vec_b.z - vec_a.z * vec_b.y,
                  vec_a.z * vec_b.x - vec_a.x * vec_b.z,
                  vec_a.x * vec_b.y - vec_a.y * vec_b.x)
docs: Return the crossproduct between vec_a and vec_b.