code: def get_vertices_per_edge(mesh_v, mesh_f):
      
  
      vc = sp.coo_matrix(get_vert_connectivity(mesh_v, mesh_f))
      result = np.hstack((col(vc.row), col(vc.col)))
      result = result[result[:,0] < result[:,1]] # for uniqueness
  
      return result
docs: Returns an Ex2 array of adjacencies between vertices, where
      each element in the array is a vertex index. Each edge is included
      only once. If output of get_faces_per_edge is provided, this is used to
      avoid call to get_vert_connectivity()