Optional rootFace: numberthe user can choose which face determines the normal direction, which for flat foldable models for example will linearize upwards or downwards depending on this chosen face's winding.
layers_face, for every layer (key), which face (value) inhabits it.
Find a topological ordering of all faces in a graph. This method is intended for 2D flat foldings. This requires the graph with folded vertices_coords, a crease pattern will not work. This method is inclusive and will include all faces from the graph in the result, even those which have no ordering. The method will first sort all faces which do have an ordering, then find any remaining faces, and add these faces in no particular order onto the beginning of the list, so that the faces with an order will be at the end (on top, painters algorithm).
a FOLD object with either faceOrders or faces_layer.