Feature parity with Python 3.14

[maxfischer2781]

Python 3.14 is out since a few months. The new features in 3.14 need to be double-checked for feature parity. Unittests must pass on 3.14, see also #188.

[maxfischer2781]

Likely relevant changes from "What's New":

• The map() function now has an optional keyword-only strict flag like zip() to check that all the iterables are of equal length.
• Add the Placeholder sentinel. This may be used with the partial() or partialmethod() functions to reserve a place for positional arguments in the returned partial object.
• Allow the initial parameter of reduce() to be passed as a keyword argument.
• The heapq module has improved support for working with max-heaps, via the following new functions: …
• The asyncio.iscoroutinefunction() is now deprecated and will be removed in Python 3.16; use inspect.iscoroutinefunction() instead.
• Calling the Python implementation of functools.reduce() with function or sequence as keyword arguments is now deprecated; the parameters will be made positional-only in Python 3.16.