Graph plotting not working properly

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Consider the following code:

def Sier(g):
    h = Graph()
    for i in range(1, g.order() + 1):
        perm = {u: (i, u) for u in g}
        gg = g.relabel(perm=perm, inplace=False)
        h.add_edges(gg.edges())
    return h

f = Sier(graphs.CompleteGraph(4))
v = f.vertices()
n1 = [((a, b), (b, a)) for a, b in v]
n2 = [(a, a), (a, a)) for a, b in v]
x = set(n1) - set(n2)
z = f.add_edges(x)
z.plot()

The plot function does not give the graph I desire. The size() function gives the size correctly. But the diagram is incorrect. Why is this? Any workarounds to make it precise?