`assert(Not)AlmostEqual(s)` specifies the type as `float`

[vnmabus]

assert(Not)AlmostEqual(s) specifies the type as float or datetime.datetime, when in practice it works also with other types that support subtraction, absolute value, rounding and comparison with zero, such as Fraction or Decimal.

This should be fixed (using TypeVar and a Protocol) to prevent Mypy errors in tests that use these types.

[srittau]

Seems reasonable. Any PRs welcome!