At the beginning, I thought it makes sense to put host ports outside the network's subgraphs to represent the machine itself, but it leads to very long edges and makes the graph hard to read. If you have the legend, it is not confusing to see the host ports near the container.

For VOLUME directives in Dockerfiles, a named Docker volume is created but with a very long hex string, giving ugly nodes

If a container belongs to multiple networks, including the default network, the later is ignored. Also record all networks in ContainerInfos for completeness

This makes the graph very difficult to read and mess up with ranks

Using : is mandatory in record shaped nodes to adress subnodes, but lead to ambiguity when used for non record nodes. So don't use : in non-record nodes, but concatenate elements to avoid ambiguity (for example between mount points with same name accross different containers)

Lot of small changes to the code : better exception handling, type hinting, fix bad variable names, docstrings etc. I am quite a beginner in Python, hopes that these changes make the code a little bit more Pythonic, more readable.