I have been investigating this:
```Python
from numbers import Real
def positive(x: Real) -> bool:
return x > 0 # Type Check failed!
```
#PEP 484 said that one should use `float` instead, but this does not solve for other numerical types e.g. #GMP numbers or #NumPy numbers.
And I found some old threads like https://github.com/python/typing/issues/1663
https://github.com/python/mypy/issues/3186
https://discuss.python.org/t/numeric-generics-where-do-we-go-from-pep-3141-and-present-day-mypy/17155
https://discuss.python.org/t/clarifying-the-float-int-complex-special-case/54018/26
And it seems like none has make any real progress.
To my understanding, ABC should also provides a good protocol for typing, just like typeclasses in #Haskell.
