try lock

At work, we have several functions that can run only one at a time. We call this "try lock" (or trylock), and had it forever in the Java code.

When we started a Python project, we wanted this functionality. A decorator seems like the right solution. The below try_lock decorator has an optional function that lets you get a finer grained solution on what to lock. It gets the function arguments and returns a key to lock on. If you don't specify keyfn, then there will be just one lock for the function.