`nx.connected_component_subgraphs(G) ` is removed by `networkx`

[baixianger]

nx.connected_component_subgraphs(G) was deprecated with version 2.1, and finally removed with version 2.4.

Instead,

Use G.subgraph(c) for c in connected_components(G)

Or G.subgraph(c).copy() for c in connected_components(G)