[DataFrame] - Add DataFrame::distinct binding

[francis-du]

Close#29

[andygrove]

Thanks @francis-du! It looks like there is a Clippy issue on all of these PRs.

[andygrove]

There are clippy failures like this - not related to your changes:

4 | default_catalog: &str,
| ^ help: if you would like to reborrow, try removing `&*`: `&`

I saw these recently on another project. We probably need to switch to using String instead of &str in pyo3 methods. Not sure why we are suddenly seeing this now though.

[francis-du]

This is a new lint in release 1.63.0
https://rust-lang.github.io/rust-clippy/master/index.html#borrow_deref_ref

I will reopen a new PR to fix this issue

[andygrove]

@francis-du could you merge latest from master on these PRs? I fixed the clippy issue

[francis-du]

@francis-du could you merge latest from master on these PRs? I fixed the clippy issue

OK 👌

[andygrove]

Looks like a linting issue

[francis-du]

Looks like a linting issue

It has been fixed, please review

[andygrove]

Thanks @francis-du!