Add type annotations

[akihironitta]

🚀 Feature

As static type checker mypy was added in #433, we can add type annotations to the codebase.

Steps to contribute

For each PR:

1. choose and remove one submodule from the list below
2. add type hints the submodule you chose
3. make sure to pass mypy check with mypy

Progress

• pl_bolts.callbacks.* (add types in bolts/callbacks #444)
• pl_bolts.datamodules.* (Adding types to some of datamodules #462)
• pl_bolts.datasets.*
• pl_bolts.losses.*
• pl_bolts.metrics.*
• pl_bolts.models.*
• pl_bolts.models.autoencoders.*
• pl_bolts.models.detection.*
• pl_bolts.models.gans.*
• pl_bolts.models.regression.*
• pl_bolts.models.rl.*
• pl_bolts.models.self_supervised.*
• pl_bolts.models.vision.*
• pl_bolts.optimizers.*
• pl_bolts.transforms.*
• pl_bolts.utils.* (Add Type Annotations to pl_bolts/utils/* #455)
• tests.*

[hassiahk]

Any help needed with this issue? I am happy to help. 😄

[akihironitta]

@hassiahk Yes! I just added the steps to contribute to the above comment, so it'd be great if you follow them and submit a PR! :]

[briankosw]

Hey @akihironitta, I'd love to help with this :) Should I just pick one and create a PR?

[akihironitta]

@briankosw Yes! Thank you!

[hassiahk]

Hey @briankosw. Yes, you can pick one and create a PR for it. 😄 Just leave a comment here saying you picked up this submodule, so you won't clash with others.

[briankosw]

I guess I'll work on pl_bolts.datamodules then!

[hassiahk]

@akihironitta, I will be working on pl_bolts.losses next. :)

[johnpeterson123]

I'm going to work on pl_bolts.optimizers now!

[akihironitta]

@johnpeterson123 Thank you for your contribution!

[jeromepatel]

I am interested in working on pl_bolts.models.regression.* .

[akihironitta]

Not sure if we want to continue on this issue because there will be a lot of # type: ignore comments in the codebase (like in #444 and #608), which I think lowers readability. Should we still keep adding type hints to Bolts?