Add public variables to __all__ in main __init__.py

[thomasaarholt]

Hiya,

I was poking around in pymc's typing, and came across this type error:

This is due to variables imported in __init__,py being "private" by default. The alternatives are either adding them under __all__ like I have done here (explicitly defining public variables) or importing them using as, for instance from .core import Backend as Backend. Since there are several variables, I chose the former.

You can read more in this documentation and this issue.

[michaelosthege]

Thanks @thomasaarholt !

Is it okay to export things that are only optionally available? (clickhouse, ClickHouseBackend)

If not, the __all__ should maybe be moved up and appended in the try block?

[thomasaarholt]

Good concern, but I've checked and we don't need to do that:

• mypy doesn't complain about it
• the entries in __all__ are strings and not the objects themselves, so that doesn't raise an error
• I've tested this at runtime, and get an error when I try to explicitly import clickhouse, but not otherwise.

[michaelosthege]

Looks like pre-commit found some trailing whitespace

[thomasaarholt]

Thanks! I squashed the commits, reset and ran precommit before re-committing. Should be good now.