graph_example: AttributeError: module 'networkx' has no attribute 'write_yaml'

[open-risk]

[PatMyron]

For posterity since this is the only search result for that error, networkx 2.6 removed those functions:
networkx/networkx#4281
networkx/networkx#4802
networkx/networkx#5345
https://networkx.org/documentation/stable/release/release_2.6.html
https://networkx.org/documentation/stable/release/migration_guide_from_2.x_to_3.0.html#deprecated-code