Lazy loading through AST-mapped public API

[Helveg]

For user convenience pretty much every module is eager loaded onto the core NEST module. This has led to circular dependencies, code execution at import time, and long import times (about 1s for me).

Using the AST module we can scan all .py files for a module level __all__ declaration, and filter out the explicitly declared parts of the public API. We can then replace all dynamic module magic of the nest module by a fully spec-supported __getattr__ approach that loads modules as attributes are requested.

On my slow IO WSL it improved import times from 1s to 0.04s. On native Linux boxes an initial test showed that it would be more like a 0.8s to 8e-05 reduction of import nest

[github-actions]

Pull request automatically marked stale!