chore(deps): update dependencies

[dandhlee]

Adding specific installation for aiplatform[prediction]. Also making the requirements.in file look nicer :)

Fixes #260.

• Tests pass
• Appropriate changes to README are included in PR

[dandhlee]

Confirmed prediction is picked up in Kokoro test from the update based on this PR:

writing output... [ 98%] prediction_v1/types
writing output... [100%] prediction_v1beta1/types

this would not show if prediction library is not installed as Sphinx would not be able to pick up on it.

[tbpg]

Why can't the library itself install these dependencies?

[dandhlee]

I have learned what they are! They are called library extras, when they're installed as like aiplatform[prediction] with extras being inside []. They are optional extras that folks can install.

Dustin filed a feature request before: pypa/setuptools#1503, but tl;dr is that with current state of python packaging, it is not possible to ask for users to install all or some extras as default when you simply install aiplatform for example. It must be explicitly done :/

[tbpg]

I guess I'm wondering if the aiplatform[prediction] library can install its necessary dependencies to generate documentation? Rather than having to do it in a generic doc generator library?

In other words, if this was a third-party library, it wouldn't make sense for it to require aiplatform[prediction].

[dandhlee]

Ah, they can! I'm just adding support for this in the mega generator in case I have to regenerate all the docs and didn't want to miss out on prediction or other smaller bits as well.

[tbpg]

Will you add a comment explaining that? Perhaps that regeneration script could install those dependencies separately?

[dandhlee]

Done! Please take a look again.