left and right sides, each side contains a list of lists of faces, groups of connected sets of faces (flaps).
Get a list of separatable flaps in a folded origami model by specifying a dividing line. The return value is two sets, one for either side of the line, each set contains a list of connected sets of faces, inside each inner array are all faces in a separatable flap.
a FOLD object with vertices in crease pattern form