How do I determine the apt package name for a given PyPI package?

Suppose I want to install a Python package system-wide on a Debian/Devuan system. Some PyPI packages have DEB packages available via the repository's apt sources, with package names prefixed by python3- (or python-, depending on Debian version). But - not all of them do. Now, I can always roll my own DEB package , but - how do I know whether my package of interest is: * actually missing; * available, but under another name (shorter form, longer-form, traditional name now changed on PyPI etc.); or * available, but bundled with other PyPI packages ? Is there a simple mapping rule, or someplace I could query with a PyPI package name and get the apt package name?