为什么曲线边在networkx中不适用于我？

Question

所以我想要有曲线边，根据documentation，这似乎非常简单，因为我可以定义connectionstyle。所以我试着建立一个最低限度的例子如下：

import numpy as np
import networkx as nx
import matplotlib.pyplot as plt

B = np.random.rand(5, 5)
G = nx.DiGraph(B)
A = nx.minimum_spanning_arborescence(G) # creating some arborescence, i.e. a directed graph

pos = nx.spring_layout(A)
nx.draw_networkx_nodes(A, pos, node_size=300)
nx.draw_networkx_edges(A, pos, connectionstyle='arc3, rad=0.2')