Bug in graphs.WheelGraph(3).show().

[漂]

sage: graphs.WheelGraph(3).is_isomorphic(graphs.CompleteGraph(3))

True

But  graphs.WheelGraph(3).show() 

show(Graph(graphs.WheelGraph(3).edges())) is OK.

So I do not know why.

[Dima Pasechnik]

It is easy to see why the plot is off for n<4, by looking at the implementation:

sage: graphs.WheelGraph??

the plotting layout is computed in the 1st 6 lines of the implementation:

    pos_dict = {}

    pos_dict[0] = (0,0)

    for i in range(1,n):

        x = float(cos((pi/2) + ((2*pi)/(n-1))*(i-1)))

        y = float(sin((pi/2) + ((2*pi)/(n-1))*(i-1)))

        pos_dict[i] = (x,y)

and it's all good for n>3, but for n<4 it's certainly not.

I've opened https://trac.sagemath.org/ticket/24512 to fix this.