[docs] Remove empty code blocks

[driazati]

This removes the linter that checks that each sphinx gallery tutorial begins with the proper boilerplate by extracting it out to sphinx gallery reset functions. This runs automatically so no code in the tutorials nor associated linters are necessary.

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[guberti]

LGTM - the empty code blocks thing has bugged me for a while.

[guberti]

For what it's worth, I've never been a fan of how we need to add the following to every tutorial:

# sphinx_gallery_start_ignore
from tvm import testing

testing.utils.install_request_hook(depth=3)
# sphinx_gallery_end_ignore

Instead, we could use reset_modules from sphinx-gallery's configuration to run code before every example. We'd add the following to docs/conf.py:

from tvm import testing
def add_hook(gallery_conf, fname):
    testing.utils.install_request_hook(depth=3)

sphinx_gallery_conf = {
    ...
    'reset_modules': (add_hook),
}

If we needed the hook for pytest as well, we could add a conf.py file to the gallery directory as well. We shouldn't change this here, but it might be worth considering in the future @driazati.

[driazati]

@guberti that makes a lot more sense, I updated the PR to use that and delete the linter which wasn't really correct anyways (some of the preamble was misplaced in a few files).

[guberti]

I love this PR.

[guberti]

This is a good change, but there's one nuance to highlight - per-file config options like sphinx_gallery_requires_cuda. If we take them out of the ignore block, the flag renders in HTML, which we do not want:

---

I can see two ways to fix this behavior. The easier, uglier way is to continue wrapping all flags in ignore blocks:

# sphinx_gallery_start_ignore
# sphinx_gallery_requires_cuda = True
# sphinx_gallery_end_ignore

This is what's done right now, and changing this may be out of scope for this pull request.

A better alternative would be updating sphinx-gallery to version 4484d35 or beyond, and then setting remove_config_comments=True in the config file. Unfortunately, 4484d35 is not part of any PyPI releases right now, making this a little more annoying.

What do you think @driazati?

[driazati]

I updated the PR to wrap the configs with ignores and made sure they are inside a code block so they don't show up on their own, so now this PR should make everything look fine from the frontend. We could merge this then update the sphinx gallery version (installing from the latest commit isn't a problem with Docker) and remove the _ignore tags.

[guberti]

Sounds good - we'll merge this, and can consider updating sphinx-gallery later. LGTM!