Incorrect type annotation for Union

[hugary1995]

I got something like

Number: typing._UnionGenericAlias  # value = typing.Union[int, float, bool]

where I expect the correct annotation to be either

Number = typing.Union[int, float, bool]

or PEP 613-style:

Number: TypeAlias = int | float | bool

I'm using version 2.5.5.

Please let me know if I was doing something wrong, or point me to the relevant source code so that I can make a PR. Thanks!