@pimms.value<EOL><INDENT>def vertex_faces(labels, vertex_face_index):<DEDENT>
return tuple([vertex_face_index[u] for u in labels])<EOL>
tess.vertex_faces is a tuple whose elements are tuples of the face indices of the faces
that contain the relevant vertex; i.e., for vertex u with vertex index i,
tess.vertex_faces[i] will be a tuple of the face indices that contain vertex u.