feat: add support and tests for struct fields

[HemangChothani]

Fixes #21

• Pyarrow version 0.17.0 has released so issue has been resolved but it doesn't support python2 so add condition for valueerror which raised when python2 excecuted.

[plamut]

Just a thought - if I understand correctly, this fix will only work in Python 3 due to the new pyarrow's incompatibility with Python 2?

If so, we might want to wait with this for a bit, since a green light was given to start transitioning the libraries to the new code generator, which also implies dropping Python 2 support.

Before this transition one final Python 2 compatible release will be made, but since this fix only affects Python 3, we might want to wait for an extra week or two, and then merge a simplified version of it.

[plamut]

It turned out there is still some work needed to transition the library to the new microgenerator (e.g. transitioning the dependencies first), which might take a while. Considering that, it's probably not worth waiting for it and getting the fix in sooner has value.

I'll review this tomorrow and see if it's good to merge and include in the next (non-major) release.

@HemangChothani It probably makes sense to conditionally bump the minimum pyarrow version to 0.17.0+ so that users on Python 3 will get the correct version that contains the fix.

[plamut]

Looks good, but we now also have to bump the minimum pyarrow version to 0.17.0 if python version >= 3.

[plamut]

LGTM, thanks for this.

Don't mind the samples, #174 contains a fix for them.

[tseaver]

@shollyman, @plamut I can't see any log for the failed Kokoro docs-presubmit job. Is that a tooling thing?

[tseaver]

On chat, I see that the Kokoro docs presubmit failures are known / expected while the infrastructure / configs get rolled out.

[tseaver]

@HemangChothani It looks like you have turned off commits from mainainers for this PR's branch, which means the automerge bot cannot "push the button" for you (nor can I).

[HemangChothani]

@tseaver I thnik that's my bad, can i merge this PR?

[plamut]

@HemangChothani In principle yes, but in the meantime @busunkim96 closed all PRs. It might be because of the CI maintenance work or something, don't know yet.