More than once I've found myself wanting to create a 'sentinel' value. The most common use case is to differentiate between an argument that has not been provided, and an argument provided with the value `None`.

This would be solvable by implementing something similar to what JavaScript calls [`Symbol`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol).

This could be implemented as a 3rd-party library, but there won't be a way to have ['Global' Symbols](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/for)

Furthermore, without a common implementation in the std library, various Python libraries had to write their own implementations, which all differs in functionality and behavior.

Is this something that the Python community is interested in? I'm willing to write the PEP