'Return the indices of the corners.
The indices are given relative to the original position of corners.
Examples
>>> from sympy.combinatorics import Permutation, Cycle
>>> from sympy.combinatorics.polyhedron import tetrahedron
>>> tetrahedron.array_form
[0, 1, 2, 3]
>>> tetrahedron.rotate(0)
>>> tetrahedron.array_form
[0, 2, 3, 1]
>>> tetrahedron.pgroup[0].array_form
[0, 2, 3, 1]
See Also
corners, cyclic_form'

@property
def array_form(self):

    corners = list(self.args[0])
    return [corners.index(c) for c in self.corners]
