py-rustworkx (spack): Rustworkx was originally called retworkx and was was created initially to be a replacement for qiskit's previous (and current) networkx usage (hence the original name). The project was originally started to build a faster directed graph to use as the underlying data structure for the DAG at the center of qiskit-terra's transpiler. However, since it's initial introduction the project has grown substantially and now covers all applications that need to work with graphs which includes Qiskit. 
Keywords: dag|graph|graph-theory|python|rust