super lightweight function registries for Python3 libraries
catalogue is a tiny, zero-dependencies library that makes it easy to add
function (or object) registries to your code. Function registries are
helpful when you have objects that need to be both easily serializable
and fully customizable. Instead of passing a function into your object,
you pass in an identifier name, which the object can use to lookup the
function from the registry. This makes the object easy to serialize,
because the name is a simple string. If you instead saved the function,
you'd have to use Pickle for serialization, which has many drawbacks.
