Graph is a project mainly written in C and PYTHON, it's free.
Default Repo description from terraform module
The cgraph module is a high performance Directed Acyclic Graph implemented in Cython. Expect graph traversals to be several hundred to thousands of times faster than Networkx for large graphs. Graph's with several hundred thousand nodes are handled with aplomb. That said, the cgraph module doesn't have near the features of Networkx. The module is designed solely for efficiently building, traversing, reversing, and introspecting large graphs. A graph theory library it is not. Most of the graph methods return iterators so that large graphs may be efficiently managed by user code.