code: def cross(triangles):
      
      vectors = np.diff(triangles, axis=1)
      crosses = np.cross(vectors[:, 0], vectors[:, 1])
      return crosses
docs: Returns the cross product of two edges from input triangles
  
      Parameters
      --------------
      triangles: (n, 3, 3) float
        Vertices of triangles
  
      Returns
      --------------
      crosses : (n, 3) float
        Cross product of two edge vectors