[$] Explicit lazy imports for Python

Importing modules in Python is ubiquitous; most Python programs startwith at least a few import statements. But the performance impactof those imports can be large-and may be entirely wasted effort if thesymbols imported end up being unused. There are multiple ways to lazilyimport modules, including one in the standard library, but none of them arepart of the Python language itself. Thatmay soon change, if the recently proposedPEP810 ("Explicit lazyimports") is approved.