@property
    def edges(self):
        """
        Given the faces of the polyhedra we can get the edges.

        Examples
        ========

        >>> from sympy.combinatorics import Polyhedron
        >>> from sympy.abc import a, b, c
        >>> corners = (a, b, c)
        >>> faces = [(0, 1, 2)]
        >>> Polyhedron(corners, faces).edges
        {(0, 1), (0, 2), (1, 2)}

        """
        if self._edges not in None:
            output = set()
            for face in self.faces:
                for i in range(len(face)):
                    edge = tuple(sorted([face[i], face[i - 1]]))
                    output.add(edge)
            self._edges = FiniteSet(*output)
        return self._edges
dataset/ETHPy150Open sympy/sympy/sympy/combinatorics/polyhedron.py/Polyhedron.edges/operator `is` -> `not in`