(triangle, edge)
return list(DiagramGrid._triangle_objects(triangle) - set(edge))[0]
Given a triangle and an edge of it, returns the vertex which
        opposes the edge.
Given a triangle and an edge of it, returns the vertex which
        opposes the edge.
Given a triangle and an edge of it returns the vertex which opposes the edge .
def _other_vertex(triangle, edge):
        """
        Given a triangle and an edge of it, returns the vertex which
        opposes the edge.
        """
        # This gets the set of objects of the triangle and then
        # subtracts the set of objects employed in ``edge`` to get the
        # vertex opposite to ``edge``.
        return list(DiagramGrid._triangle_objects(triangle) - set(edge))[0]
def _other_vertex ( triangle , edge ) : # This gets the set of objects of the triangle and then # subtracts the set of objects employed in ``edge`` to get the # vertex opposite to ``edge``. return list ( DiagramGrid . _triangle_objects ( triangle ) - set ( edge ) ) [ 0 ]