fix: add type hint for progress_bar_type in read_gbq function

[haru-256]

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Fixes #934

[haru-256]

@Genesis929
Could you please review this?

[chalmerlowe]

@Genesis929 Could you please review this?

@haru-256:

I am the maintainer (along with @Linchin) of this library. @Linchin and I decide what gets accepted or not.

@Linchin asked a question about this problem on Issue #934 but they did not get a response:

Can you tell us more about how the error was raised? Was it blocking you from executing the code, or it's a notification from your IDE?

Please be aware that:

• We do not enforce or check type hinting in this library (although some parts of the code, for good or bad, have legacy type hints).
• We do not guarantee that we will support type hinting.
• We do not have the addition of type hint CI/CD checks on our roadmap.
• If the code fails to execute under normal use cases, that is one thing, but failing due to a type hinter that we don't use OR guarantee is not a priority.

In looking at the merits of this PR, it is not testable under our current infrastructure, since we don't have type hinting in our CI/CD pipeline.

Why do I go on about type hinting? In looking at the error you posted:

Argument of type "None" cannot be assigned to parameter "progress_bar_type" of type "str" in function "read_gbq"
"None" is not assignable to "str"

The error message appears to be from the pyright tool maintained by Microsoft.

Here is a similar example.

pyright: Argument of type "Literal[1]" cannot be assigned to parameter "x" of type "str" in function "f"

Here is a link to the strings that generate that style of error message: https://github.com/microsoft/pyright/blob/5ba9dcf9802382b4db529221ba353ae3edc597ad/packages/pyright-internal/src/localization/package.nls.en-us.json#L43

Mypy uses a slightly more cryptic verbiage:

mypy: Argument x to "f" has incompatible type "int"; expected "str"

[haru-256]

Sorry for the late reply, I missed this notification.
I understand that you are not planning to support type hints.

Thank you