sinpledispatchmethod for old version python

singledispatchmethod.py

try:
    # python 3.8 or later
    from functools import singledispatchmethod
except ImportError:
    from functools import singledispatch, update_wrapper

    def singledispatchmethod(func):
        dispatcher = singledispatch(func)
        def wrapper(*args, **kw):
            return dispatcher.dispatch(args[1].__class__)(*args, **kw)
        wrapper.register = dispatcher.register
        update_wrapper(wrapper, func)
        return wrapper